What fluids can you drink when fasting? A comprehensive guide for nutrition and wellness

October 30, 2025 •

4 min read

While on an intermittent fasting regimen, you can consume certain calorie-free beverages without breaking your fast, aiding hydration and hunger management. Learning what fluids can you drink when fasting is essential for maintaining the benefits, such as weight loss and metabolic improvements, without disrupting the body's fasted state.

Quick Summary

This article explores the approved fluids for maintaining a fast, focusing on zero-calorie options like water, black coffee, and unsweetened teas. It details how certain beverages can support hydration and curb appetite, while others must be avoided due to calorie or sugar content. The guide also addresses the role of electrolytes, especially during longer fasts, to prevent dehydration.

Key Points

Stick to Calorie-Free Fluids: To maintain a fasted state, consume only beverages that contain zero calories, such as plain water, black coffee, and unsweetened tea.
Water is a Priority: Hydration is crucial during fasting, with plain or mineral water being the best choice for flushing toxins and curbing hunger.
Avoid Sugary Additives: Adding sugar, milk, cream, or caloric sweeteners to coffee or tea will break your fast by causing an insulin spike.
Consider Electrolytes for Longer Fasts: For extended fasting periods, using bone broth or zero-calorie electrolyte supplements can help replenish lost minerals and prevent symptoms like fatigue and headaches.
Be Cautious with Artificial Sweeteners: The impact of zero-calorie sweeteners on fasting is debated; if you are strict about your fast, it's best to avoid them as they may cause cravings.
Moderation with Caffeine: While black coffee is generally fine, excessive caffeine on an empty stomach can lead to jitters or digestive upset, so monitor your intake.
Read Labels Carefully: Always check the ingredients list on bottled beverages like flavored sparkling water to ensure they don't contain hidden sugars or additives.
Bone Broth is a Gray Area: While it technically contains calories, bone broth is often used in longer fasts for its electrolyte content. However, for a true, strict fast, it should be avoided.

The practice of fasting, particularly intermittent fasting, has gained popularity for its potential health benefits, including weight loss, metabolic health, and cellular repair (autophagy). However, to reap these benefits, it's crucial to understand which fluids you can consume without breaking your fast. The key principle is to avoid anything with significant calories, as this triggers an insulin response that signals your body to exit the fasted, fat-burning state.

The Golden Rule of Fasting Fluids: Go Calorie-Free

The fundamental guideline for what to drink while fasting is simple: stick to zero-calorie beverages. This ensures you remain in a fasted state, allowing your body to continue burning fat and undergoing cellular repair.

Acceptable Fasting-Friendly Fluids

Plain Water: This is the most essential and recommended fluid for any fast. Water provides hydration without any calories and can help curb hunger pangs. Options include plain tap, purified, or mineral water.
Sparkling Water: As long as it is unsweetened and free of artificial flavors or additives, sparkling water is an excellent calorie-free alternative to plain water.
Black Coffee: For many, black coffee is a lifesaver during a fast. It contains a negligible amount of calories (about 3-5 per cup) and can help suppress appetite and boost metabolism. However, adding sugar, milk, or cream will break your fast.
Unsweetened Tea: Like coffee, plain tea without milk, sugar, or honey is an acceptable option. Green, black, white, and herbal teas are generally fine. Some herbal teas, such as green tea and ginger tea, even offer additional metabolic benefits.
Bone Broth (for longer fasts): While it contains some calories, bone broth is often permitted during extended fasts (24 hours or longer). A small amount provides essential electrolytes and minerals, which can help mitigate the side effects of fasting and rehydrate the body without causing a significant insulin spike.
Diluted Apple Cider Vinegar (ACV): A small amount (1-2 teaspoons) of apple cider vinegar mixed into water can aid digestion, regulate blood sugar, and reduce cravings, all while keeping calories to a minimum.

The Role of Electrolytes During Prolonged Fasting

During longer fasts, the body naturally flushes out fluids and electrolytes like sodium, potassium, and magnesium. This can lead to what is sometimes called the "keto flu," causing symptoms like fatigue, headaches, and muscle cramps.

Electrolyte supplementation is crucial during extended fasts. You can replenish lost minerals with:

Bone Broth: As mentioned, it's a natural source of electrolytes.
Himalayan Pink Salt: Adding a pinch of Himalayan salt to your water can help replenish sodium and other trace minerals.
Electrolyte Supplements: Many zero-calorie electrolyte powders and tablets are designed specifically for fasting, ensuring you get the minerals you need without breaking your fast.

Fluids to Avoid While Fasting

To ensure you don't accidentally break your fast, it is essential to avoid the following drinks:

Sugary drinks: This includes sodas, fruit juices (even freshly squeezed), and sweetened iced teas.
Milk and Cream: Dairy products contain calories and lactose, which can trigger an insulin response.
Flavored Coffee/Tea with Additives: Anything with added syrups, sugar, or flavorings should be avoided.
Alcohol: All forms of alcohol contain calories and carbs and can interfere with a fasting state.
Diet Soda (Controversial): While technically zero-calorie, artificial sweeteners can sometimes trigger an insulin response or increase cravings, undermining the fast. It is best to avoid them if you are fasting strictly.

Comparison of Fasting-Friendly Fluids


Beverage	Calorie Content	Impact on Fast	Notes
Plain Water	0	None	Essential for hydration. Can be plain, mineral, or sparkling.
Black Coffee	3-5 per cup	Minimal	Can boost metabolism and suppress appetite. Avoid all additives.
Herbal Tea	0	None	Can soothe digestion and offer antioxidants. Ensure it's unsweetened.
Bone Broth	~20-60 per cup	Minor, acceptable for longer fasts	Provides electrolytes and minerals. Check for low-calorie, high-quality options.
ACV Water	~3-6 per tsp	Minimal	May help with blood sugar and cravings. Drink through a straw to protect teeth.
Sugary Drinks	High	Breaks fast	Triggers an insulin spike and ends the fasted state.
Milk/Cream	Variable	Breaks fast	Adds calories and lactose, causing an insulin response.

Practical Tips for Success

Start Your Day Right: Begin your fasting window with a large glass of water. Adding a squeeze of lemon can add flavor without calories.
Moderate Your Caffeine: While coffee can be beneficial, excessive caffeine intake on an empty stomach can cause jitters or digestive issues. Listen to your body and limit your intake to a few cups.
Stay Mindful of Additives: Always read the labels of any pre-packaged fluids like flavored water or electrolytes to ensure they don't contain added sugars or artificial sweeteners that could break your fast.
Listen to Your Body: Pay attention to how different fluids affect you. Some people may find that even a small amount of caffeine is too much on an empty stomach, while others tolerate it well. Adjust your fluid choices based on your personal needs and how you feel.

Conclusion

Knowing what fluids you can drink when fasting is vital for a successful fasting regimen. By focusing on zero-calorie options like water, black coffee, and unsweetened teas, you can stay hydrated, manage hunger, and maximize the benefits of fasting. For longer fasts, incorporating electrolyte-rich fluids like bone broth or supplements can help prevent imbalances. Always be mindful of hidden calories and additives in your beverages and listen to your body's signals to ensure a safe and effective fasting experience. Ultimately, proper hydration with the right fluids is a cornerstone of a successful nutrition diet incorporating fasting.

Outbound Link

For more detailed information on the metabolic effects of different food and drinks on a fast, including a deeper look into the debated topic of artificial sweeteners, you can consult this resource from a leading health institute: What Breaks a Fast? Foods, Drinks, and Supplements.

Frequently Asked Questions

While diet sodas are calorie-free, the artificial sweeteners they contain can sometimes trigger an insulin response or increase cravings in some individuals, potentially undermining the benefits of a strict fast. For best results, it is often recommended to avoid them.

A small amount of lemon juice squeezed into plain or sparkling water is generally considered acceptable. The minimal calories are not enough to break a fast, and it can add flavor and aid in hydration. However, adding any form of sugar will break the fast.

Yes, bone broth technically breaks a fast because it contains calories from protein and fat. However, it is often used during longer, modified fasts to provide electrolytes and nutrients without causing a significant insulin spike. For a strict, zero-calorie fast, it should be avoided.

No, adding milk, cream, or sugar to your tea will break your fast. These additives contain calories and can trigger an insulin response, which ends the body's fasted state.

Moderate consumption of black coffee is generally acceptable, with many fasters enjoying 1-3 cups per day. Excessive intake can cause side effects like jitters or digestive discomfort due to an empty stomach.

Bulletproof coffee, which includes butter and MCT oil, contains calories and therefore breaks a traditional fast. While some people on a ketogenic diet may use it, it prevents the body from entering a fully fasted state and limits benefits like autophagy.

For longer fasts, you can get electrolytes without calories by adding a pinch of Himalayan pink salt to your water or using a zero-calorie electrolyte supplement designed for fasting. Bone broth is another option, though it contains some calories.