What is the best drink to have while fasting? A comprehensive guide

November 19, 2025 •

4 min read

According to Johns Hopkins neuroscientist Mark Mattson, the body starts burning fat after hours without food, a process known as metabolic switching. Choosing the right beverages is essential to sustain this state, which is why understanding what is the best drink to have while fasting is crucial.

Quick Summary

Calorie-free and zero-carbohydrate beverages like water, black coffee, and unsweetened tea are the top choices for maintaining a fasted state. Zero-calorie electrolyte drinks can also support hydration during longer fasts.

Key Points

Plain Water is Primary: The safest and most essential drink while fasting is plain water, as it is calorie-free and vital for hydration.
Stick to Zero Calories: Black coffee, unsweetened herbal tea, and sparkling water are excellent zero-calorie options that will not break a fast.
Mind the Add-Ins: Any additions like sugar, milk, cream, or caloric sweeteners will break your fast and should be avoided.
Electrolytes for Longer Fasts: For extended fasts or during exercise, zero-calorie electrolyte drinks are recommended to prevent dehydration and mineral imbalance.
Check Labels for Sweeteners: Be cautious with diet sodas and flavored waters, as artificial sweeteners can sometimes trigger metabolic responses or cravings.
Avoid Sugary Beverages: Drinks like soda, juice, milk, and smoothies contain calories and sugar, which will end your fast and its benefits.

The Safest Choices: Zero-Calorie Essentials

When adhering to a strict fast, the primary goal is to avoid any calories that could trigger an insulin response and break the fasted state. The safest and most reliable options are those with zero calories and no added sugars.

The Power of Plain Water

Water is the cornerstone of a successful fast. It is entirely calorie-free and serves multiple vital functions during a period of caloric restriction:

Prevents Dehydration: Fasting can increase urination, making proper hydration critical to avoid fatigue, headaches, and dizziness.
Manages Hunger: Drinking plenty of water can help fill the stomach and reduce the sensation of hunger.
Supports Bodily Functions: Water is essential for regulating body temperature, lubricating joints, and keeping organs functioning properly.

Both still and sparkling water are acceptable options, provided they are unsweetened and without added flavors that contain calories.

The Perks of Black Coffee

For many, black coffee is a valuable tool during a fast. When consumed without sugar, cream, or milk, it contains minimal calories (typically less than 5 per cup) and offers several benefits:

Appetite Suppression: The caffeine in black coffee can help curb hunger, making it easier to stick to your fasting schedule.
Energy Boost: It provides a stimulant effect that can increase alertness and focus.
Metabolism Enhancement: Some research suggests caffeine can boost metabolism and increase fat oxidation.

It's important to consume black coffee in moderation, as too much can cause acidity or anxiety.

Unsweetened Teas: Green and Herbal

Unsweetened teas are excellent calorie-free alternatives to water and coffee. They can help with hydration and provide a variety of health benefits:

Green Tea: Rich in antioxidants, especially epigallocatechin gallate (EGCG), green tea can enhance metabolism and improve insulin sensitivity.
Herbal Tea: Many herbal teas, such as chamomile, peppermint, and ginger, are naturally caffeine-free and offer calming effects or aid digestion. Always ensure the tea is free from added sweeteners.

More Nuanced Options: The Flexible Fast

While purists stick to zero-calorie options, some practitioners of less restrictive fasting might consider beverages with minimal caloric impact, depending on their specific goals.

Zero-Calorie Electrolyte Drinks

For longer fasts, especially those over 16 hours or combined with exercise, supplementing with electrolytes can prevent depletion and associated symptoms like muscle cramps, fatigue, and headaches.

Electrolytes like sodium, potassium, and magnesium can be replenished with zero-calorie powders or drops added to water.
Crucially, check the label to ensure no sugar or caloric ingredients are included, as many commercial sports drinks are packed with sugar.

Diluted Apple Cider Vinegar (ACV)

Some people find that diluting 1–2 teaspoons of apple cider vinegar in a large glass of water can help curb cravings and regulate blood sugar. Always dilute ACV sufficiently and consider drinking it through a straw to protect tooth enamel from its acidity.

Comparison of Fasting-Friendly Drinks


Drink	Calorie Count	Caffeine	Hydration	Appetite Control	Electrolytes	Comments
Plain Water	Zero	No	Excellent	Low	No	The safest, most essential drink.
Sparkling Water	Zero	No	Excellent	Moderate	No	Can help with feelings of fullness due to carbonation.
Black Coffee	Minimal	Yes	Moderate	High	No	Provides an energy and focus boost; watch for acidity.
Unsweetened Teas	Zero	Low/No	Excellent	Low/Moderate	No	Offers antioxidants and variety without breaking the fast.
Zero-Calorie Electrolyte Drinks	Zero	No	Excellent	Low	Yes	Crucial for longer fasts, preventing mineral depletion.
Diluted ACV	Minimal	No	Good	Moderate	No	May help regulate blood sugar and cravings; dilute to protect teeth.

Drinks That Will Break Your Fast

Any beverage containing significant calories or sugars will effectively end a fast by triggering an insulin response. These drinks should be avoided during your fasting window:

Sugary Sodas and Juices: These cause rapid blood sugar and insulin spikes, completely negating the metabolic benefits of fasting.
Milk and Creamers: Milk contains sugar and protein, and adding it to coffee or tea introduces calories that break a fast.
Protein Shakes and Smoothies: While nutritious during eating windows, these are calorie-dense and will break a fast immediately.
Bone Broth: Contains protein and calories, which will interrupt a clean fast. It is, however, an excellent source of electrolytes and nutrients for breaking a fast gently.
Alcohol: Contains empty calories and can interfere with the metabolic process while increasing dehydration.

How to Hydrate Effectively While Fasting

Sip, Don't Gulp: Spread your fluid intake throughout the day rather than consuming large amounts at once.
Listen to Your Body: If you feel lightheaded, nauseous, or have muscle cramps, it may be a sign of dehydration or electrolyte imbalance.
Check Ingredients: Be vigilant about reading labels on flavored waters, sports drinks, and any zero-calorie drinks, as some artificial sweeteners can potentially affect insulin or cause cravings.
Start Simple: For beginners, sticking to plain water is the safest and easiest way to ensure you don't accidentally break your fast. You can explore other options as you become more comfortable with your routine. For more information on fasting and its benefits, consult resources from Johns Hopkins Medicine.

Conclusion

Ultimately, what is the best drink to have while fasting is plain, calorie-free water for hydration and metabolic health. For those seeking variety or additional benefits, black coffee, unsweetened teas, and sugar-free electrolyte supplements are excellent and safe choices. The key is to avoid any drink with calories or sugar to maintain the fasted state and maximize your health benefits.

Frequently Asked Questions

Consuming any drink with calories or carbohydrates will trigger an insulin response, which effectively breaks your fast. This stops the metabolic processes associated with fasting, like fat burning.

This is a debated topic. While diet sodas are calorie-free, some artificial sweeteners may provoke an insulin response or increase cravings for sugar. To be safe, many fasting experts recommend sticking to natural, unsweetened beverages.

No, bone broth contains calories and protein, so it will break a clean fast. It is, however, an excellent, nutrient-dense choice for when you are ready to break your fast, as it contains electrolytes and is gentle on the digestive system.

Adding a small slice of lemon or a splash of lemon juice to water is generally considered acceptable and will not break your fast, as it contains a negligible amount of calories. However, be cautious not to use too much.

Some electrolyte products contain sugar and calories, but many zero-calorie versions are available for fasting. Always check the nutrition label to ensure it is free of added sugars and caloric ingredients.

Yes, green tea contains some caffeine but in lower amounts than coffee. It is perfectly acceptable for fasting, provided it is unsweetened. The antioxidants in green tea offer additional health benefits.

You should consider drinking electrolytes, such as from zero-calorie powders, during longer fasts (e.g., 24+ hours) or when exercising while fasting. This helps prevent fatigue, headaches, and muscle cramps due to mineral depletion.