What drinks can you have when fasting? A guide to staying hydrated without breaking your fast

October 25, 2025 •

5 min read

According to Johns Hopkins neuroscientist Mark Mattson, our bodies are built to withstand periods without food, which triggers a metabolic switch to burn fat for energy. This metabolic flexibility is key to reaping the benefits of fasting, but it can be easily disrupted by consuming the wrong things. Staying properly hydrated with the right choices is crucial, and this guide provides clarity on what drinks can you have when fasting to support your goals.

Quick Summary

The most effective way to sustain a fast is by consuming strictly calorie-free beverages like water, plain coffee, and unsweetened teas. Drinks containing any sugar, milk, or artificial sweeteners should be avoided to prevent a metabolic response that halts the fasting process. Proper hydration is essential for avoiding side effects like headaches and dizziness. Modifying strict rules depends on individual goals, but caution is advised.

Key Points

Stick to zero calories: The safest options for fasting are strictly calorie-free beverages like water, black coffee, and plain unsweetened tea.
Prioritize hydration: Drinking plenty of water is essential to prevent dehydration, headaches, and fatigue, which are common side effects of fasting.
Black coffee is your friend: Enjoying plain, black coffee can provide a useful energy boost and suppress appetite without breaking your fast.
Avoid sugary additives: Any sugar, honey, milk, cream, or other high-calorie additives in your drinks will trigger an insulin response and break your fast.
Be cautious with artificial sweeteners: While calorie-free, these sweeteners can sometimes cause cravings or a metabolic reaction in some people, so it is best to avoid them.
Listen to your body: If you choose to incorporate low-calorie items like lemon water or electrolytes, pay attention to how your body responds and adjust based on your specific fasting goals.

The Golden Rule of Fasting: The Zero-Calorie Principle

At its core, a fast is defined by a period of abstaining from caloric intake to promote metabolic changes, such as shifting the body from burning glucose to burning stored fat for energy. The simplest rule to follow is to stick to zero-calorie beverages. This ensures that you don't trigger an insulin response or interrupt the physiological state your body enters during a fast. While the definition of what 'breaks a fast' can vary slightly depending on your specific goals, maintaining a calorie-free beverage intake is the safest and most reliable approach for most fasters.

The Safest Beverages for Your Fasting Window

These drinks are universally considered safe and will not interfere with your fasted state. They are essential for staying hydrated and managing hunger.

Plain Water (Still, Mineral, and Sparkling): This is the foundation of hydration, and you should drink plenty of it throughout your fast. Water helps with bodily functions, flushes out waste, and can suppress hunger pangs. Mineral and sparkling water are also acceptable, as long as they contain no added sweeteners or calories.
Black Coffee: For many, black coffee is a crucial part of their fasting routine. It's virtually calorie-free and the caffeine can act as an appetite suppressant and energy booster. Just remember to keep it plain—no sugar, milk, cream, or other additives.
Unsweetened Tea: Black, green, and herbal teas are excellent options. They offer flavor variety without calories, and green tea, in particular, may offer additional health benefits. Ensure your tea is free of any added sugar or honey. If using a pre-packaged variety, check the ingredients list to confirm it's unsweetened.

Controversial and Modified Fasting Drinks

Some drinks exist in a grey area, and their suitability depends on how strictly you adhere to your fast. These options introduce a minimal amount of calories or other compounds that might affect the metabolic state.

Lemon Water: Adding a small amount of lemon juice to water is popular for flavor. A few slices or a small squeeze contains only a few calories, which most strict fasters would avoid, but many find it does not significantly impact their fast. Use your discretion and monitor how your body responds.
Electrolyte Water: During extended fasts, you can lose essential electrolytes. Some fasters add a pinch of Himalayan pink salt or a small amount of an electrolyte powder to their water. This technically has calories but can help prevent symptoms of dehydration and electrolyte imbalance.
Apple Cider Vinegar (ACV): Diluted ACV is sometimes consumed during a fast for its potential metabolic benefits. A small amount of diluted ACV is low in calories, but like lemon water, it's not strictly zero-calorie. The effect on blood sugar is minimal, but individual responses can vary.

Comparison of Fasting Drinks and Their Effects


Drink	Zero-Calorie	Strict Fast Safe	Modified Fast Possible	Benefits	Drawbacks/Cautions
Plain Water	Yes	Yes	Yes	Hydrates, flushes waste, no metabolic impact	None
Black Coffee	Yes	Yes	Yes	Appetite suppressant, energy boost	Can be hard on an empty stomach; too much can cause jitters
Unsweetened Tea	Yes	Yes	Yes	Antioxidants, hydration, can be calming	Caffeine can be a diuretic; ensure no additives
Lemon Water	Minimal	No	Yes	Contains Vitamin C and potassium, adds flavor	Technically breaks a strict fast; small calorie count
Electrolyte Water	Minimal	No	Yes	Replenishes lost minerals during long fasts	Technically breaks a fast; monitor ingredients for calories
Bone Broth	Minimal	No	Yes	Replenishes electrolytes; contains protein and fat	Contains calories and protein, definitely breaks a strict fast
Diet Soda	No	No	Depends	Zero calories but uses artificial sweeteners	Can cause cravings or insulin response in some; best to avoid

Drinks to Avoid While Fasting

For a successful fast, it's just as important to know what to avoid. These beverages can quickly negate the metabolic benefits of your fasting window.

Sugary Sodas and Juices: Both are loaded with calories and sugar, causing a rapid spike in blood sugar and an insulin response that immediately breaks your fast. Even fruit juices, which are often perceived as healthy, are concentrated sources of sugar that should be avoided.
Dairy and Creamers: Adding milk, cream, or other dairy products to your coffee or tea adds calories and fat, ending your fasted state. The amount of milk required to break a fast is minimal, so even a 'splash' is generally not recommended for purists.
Alcohol: All alcoholic beverages contain calories and carbohydrates that will break a fast. Additionally, consuming alcohol on an empty stomach can be harmful and has a more pronounced effect.
Sweetened Beverages: This includes lattes, energy drinks, and any packaged beverage with added sugar or sweeteners. The high sugar content is counterproductive to fasting goals.
Artificial Sweeteners: Even though they contain zero calories, artificial sweeteners can trigger an insulin response or cause cravings in some individuals, potentially disrupting the metabolic goals of the fast. It's best to avoid them to be safe.

The Importance of Hydration

Dehydration is one of the most common and uncomfortable side effects of fasting, leading to headaches, dizziness, and fatigue. The body excretes more water and electrolytes during a fast, so prioritizing fluid intake is vital. Beyond just water, incorporating the low-calorie options mentioned above can help you meet your hydration needs and make the fast more bearable. When you're adequately hydrated, you're more likely to manage hunger and stick to your fasting schedule. Experts recommend consuming around 2-3 liters of fluids per day during a water-based fast.

Conclusion

For those wondering what drinks can you have when fasting, the simplest and most effective answer is to stick to calorie-free options. Plain water, black coffee, and unsweetened teas are the safest bets for maintaining a fasted state and reaping its full benefits. While some may choose to include a small amount of lemon juice, electrolytes, or even bone broth in a modified approach, this depends on individual goals and how strictly one defines their fast. What is non-negotiable is avoiding all forms of added sugar, dairy, alcohol, and sweeteners, as they will undoubtedly break the fast and interrupt the metabolic processes at play. By focusing on smart hydration with approved beverages, you can support your body's natural fasting state and achieve your health objectives.

Note: Before beginning any fasting regimen, especially extended fasts, it is always recommended to consult with a healthcare professional.

Frequently Asked Questions

Most experts recommend avoiding diet soda during a fast. While calorie-free, the artificial sweeteners can trigger a cephalic-phase insulin response and increase cravings in some people, which can interfere with the goals of fasting.

No, adding milk or cream to your coffee will break your fast. Both contain calories, fat, and protein that will trigger a metabolic response, effectively ending your fasted state.

A small amount of lemon juice is unlikely to significantly impact your fast, but it does contain a few calories. Strict fasters typically avoid it, while others find the small amount acceptable. Use your own discretion and monitor your body's response.

Unsweetened herbal tea is generally fine. Options like chamomile, peppermint, or ginger tea are calorie-free and can provide flavor and hydration without breaking your fast.

Bone broth contains protein and a small amount of calories, which will technically break a strict fast. It is often recommended as a way to gently break a longer fast or used in modified fasting protocols for electrolytes, but not for maintaining a strict fast.

Hydration is crucial because fasting can lead to a loss of fluids and electrolytes, which can cause symptoms like headaches, fatigue, and dizziness. Drinking enough water supports your body's functions and helps manage hunger.

The best drinks to break a fast are gentle on the digestive system. Water or a mineral-rich beverage like bone broth or electrolyte water are excellent choices. Avoid sugary drinks or large quantities of liquids right away.