What Drinks Are Allowed During Intermittent Fasting? Your Ultimate Guide

October 12, 2025 •

4 min read

According to research from Johns Hopkins University, intermittent fasting can provide numerous health benefits, including weight loss and improved metabolic function. To maximize these effects, it is crucial to understand what drinks are allowed during intermittent fasting and which can unexpectedly break your fast.

Quick Summary

During intermittent fasting, the primary rule is to consume only zero-calorie or near-zero-calorie beverages to maintain the fasted state. Recommended options include plain water, black coffee, and unsweetened teas. Some zero-calorie drinks, like those with artificial sweeteners, are a topic of debate due to potential metabolic effects. Certain beverages containing calories, sugar, or protein must be avoided completely during fasting windows.

Key Points

Prioritize Zero Calories: The fundamental rule is to consume only zero-calorie drinks like water, black coffee, and unsweetened teas to avoid breaking your fast.
Stay Hydrated with Water: Water is essential for maintaining proper hydration during fasting and can be enhanced with natural flavors like lemon or mint.
Avoid Sweet Additives: Adding sugar, milk, honey, or cream to coffee and tea will break your fast by triggering an insulin response.
Approach Diet Drinks with Caution: Artificial sweeteners in diet sodas are controversial, as they may trigger metabolic responses or cravings, potentially compromising the benefits of a strict fast.
Replenish Electrolytes for Longer Fasts: For longer fasting periods or during exercise, unsweetened electrolyte supplements can be crucial to prevent imbalances without breaking the fast.
Limit "Dirty Fasting" : While some allow for minimal calories (a "dirty fast"), this can interfere with benefits like autophagy and is not recommended for strict fasting goals.
Stick to a Healthy Eating Window: The drinks you consume during your eating window also matter, so focus on nutritious choices to support your overall health goals.

The Golden Rule: Stay at Zero Calories

Intermittent fasting works by prolonging the period when your body has burned through its sugar stores and begins to burn fat for energy. This process, known as metabolic switching, is a key benefit of fasting. To maintain this state, the golden rule for liquids is to consume as few calories as possible, ideally none. While consuming a small amount of calories, often cited as under 50, might not completely halt the fat-burning process for some, it is best to stick to zero calories to avoid triggering an insulin response that could interfere with your fasting goals.

The Essentials: Water, Coffee, and Tea

Staying hydrated is non-negotiable during your fasting window. Dehydration can lead to fatigue, headaches, and increased hunger, which can derail your progress.

Water: The most fundamental fasting beverage. This includes still, sparkling, and mineral water. Water has zero calories and is essential for all bodily functions. For a flavor boost without breaking your fast, you can add a few slices of lemon or cucumber, or a sprig of mint.
Black Coffee: Unsweetened, plain black coffee is widely accepted as a fasting-friendly drink. It contains a negligible amount of calories (about 3-5 per cup) and can offer a caffeine boost to help suppress appetite and increase mental alertness. Decaf coffee is also a safe option for those sensitive to caffeine. However, adding sugar, milk, or flavored creamers will break your fast and should be avoided.
Unsweetened Tea: Like coffee, most teas are a fantastic fasting beverage as long as they are unsweetened. This includes:
- Green Tea: Contains antioxidants and may help boost metabolism.
- Black Tea: Also contains antioxidants and can be a good energizer.
- Herbal Tea: Caffeine-free options like chamomile, peppermint, and ginger are great for hydration and can be soothing.

The Controversial Corner: Artificial Sweeteners and Diet Sodas

The use of artificial sweeteners and diet sodas during fasting is highly debated. While they are calorie-free, their sweet taste can trigger a cephalic phase insulin response in some individuals, potentially reducing the metabolic benefits of fasting. The sweet taste can also increase cravings and activate the digestive system.

Sucralose, Aspartame, and Stevia: While some studies show minimal effect on insulin, others suggest a potential disruption, especially for those with specific health goals like improving insulin sensitivity. For a strict fast aiming for autophagy (cellular cleanup), it is best to avoid all sweeteners.
Diet Soda: The artificial sweeteners and other additives in diet soda can pose a risk of breaking a strict fast. Although calorie-free, they may trigger metabolic responses or harm the gut microbiome. Opting for sparkling water with a natural flavor essence is a safer alternative.

Specialized Fasting Drinks

For longer fasts, certain low-calorie options can help replenish essential minerals and make the experience more comfortable.

Bone Broth: Contains calories and protein, so it will break a strict fast aimed at autophagy. However, some intermittent fasting protocols, particularly those focused on fat loss, permit a small amount of bone broth during the fasting window to provide electrolytes and curb hunger. It is important to note this is a "dirty fast" and not suitable for all fasting goals.
Electrolyte Supplements: During extended fasting, the body loses electrolytes (sodium, potassium, magnesium) due to decreased insulin levels. Unsweetened electrolyte supplements can be added to water to prevent imbalances and symptoms like headaches, fatigue, and muscle cramps. Make sure they are truly calorie-free with no added sugar.
Diluted Apple Cider Vinegar (ACV): A small amount of ACV diluted in water is a low-calorie option some use to help curb appetite and support digestion.

Comparison of Common Beverages During Intermittent Fasting


Drink	Calories	Insulin Impact	Fasting Status (Strict IF)	Notes
Plain Water	0	None	Allowed	Essential for hydration.
Black Coffee	3-5 (negligible)	Minimal to None	Allowed	Do not add sugar or cream.
Unsweetened Tea	~2 (negligible)	Minimal to None	Allowed	Green, black, and herbal are fine.
Water with Lemon Slices	~4 (negligible)	Minimal to None	Generally Allowed	Lemon itself has low calories.
Sparkling Water	0	None	Allowed	Opt for plain, unsweetened.
Diet Soda	0	Debated	Not Recommended	Can cause insulin response or cravings.
Sugary Soda	High	High	Breaks Fast	Contains high sugar and calories.
Fruit Juice	High	High	Breaks Fast	Contains natural sugars and calories.
Milk/Creamer	Moderate to High	Moderate to High	Breaks Fast	Protein and sugar trigger insulin.
Bone Broth	~40-50	Moderate (protein)	Breaks Strict Fast	Considered for "dirty fasts" only.

What To Avoid Entirely

Any drink with a significant calorie count or a high sugar content will break your fast. This list includes:

Sugary Soft Drinks: Regular sodas and energy drinks are loaded with sugar and will cause a significant insulin spike.
Fruit Juice: Despite being natural, fruit juice contains concentrated sugar that is metabolized similarly to soda and will break your fast.
Alcohol: All forms of alcohol contain calories and are processed by the liver, which interrupts the fasted state.
Milk and Creamers: Whether dairy or plant-based, milk and creamers contain calories from protein and sugar (lactose), which will prompt an insulin response.
Sweetened Teas and Coffees: Any beverages with added sugar, honey, or syrup should be avoided.

Conclusion

For intermittent fasting, the safest and most effective strategy for beverages is to stick to zero-calorie options like water, black coffee, and unsweetened teas. These choices support hydration and help maintain the metabolic state of fasting without interfering with its benefits. While some gray-area drinks like diet soda exist, their potential to trigger an insulin response or cravings makes them a risky choice for those pursuing a strict fast. Remember to listen to your body and choose beverages that support your specific fasting goals, and for personalized advice, consult with a healthcare professional.

For more detailed information on intermittent fasting and its benefits, you can refer to the resources provided by the reputable medical institution, Johns Hopkins Medicine.

Frequently Asked Questions

No, plain black coffee contains a negligible amount of calories and is widely considered acceptable during an intermittent fasting window. However, adding sugar, milk, or cream will break the fast.

Yes, unsweetened teas like green, black, or herbal tea are excellent choices during your fasting window. Ensure no sugar, honey, or milk is added to maintain the fasted state.

This is a debated topic. While diet sodas contain no calories, the artificial sweeteners can trigger an insulin response or increase cravings in some people. For a stricter fast, it's best to avoid them and stick to water or unsweetened tea.

Yes, bone broth contains calories and protein, which will break a strict fast, especially if your goal is autophagy. Some intermittent fasting methods allow it for fat loss goals, but it is not a zero-calorie option.

Yes, adding a few slices of lemon to your water is generally acceptable. The minimal calories from the lemon are unlikely to significantly impact your fasted state.

A small amount of diluted apple cider vinegar is often permitted during fasting. It's a low-calorie option that may help with appetite control and can be beneficial.

Yes, especially during longer fasts or intense exercise, as fasting can lead to electrolyte loss. Using an unsweetened, zero-calorie electrolyte supplement is a recommended way to replenish essential minerals without breaking your fast.