What Should You Put in Water When Fasting for Better Hydration and Electrolytes?

November 15, 2025 •

4 min read

The human body is over 60% water, and staying hydrated is critical during any fast, especially longer ones. Knowing what should you put in water when fasting can make the difference between a successful fast and feeling fatigued, dizzy, or experiencing other side effects from electrolyte imbalance.

Quick Summary

This guide details safe and effective, calorie-free additions to water while fasting. Replenish electrolytes with salt, add flavor with lemon or herbs, and use apple cider vinegar to curb appetite. It also covers drinks and supplements to avoid to maintain the fasting state.

Key Points

Electrolyte Replenishment: Add a pinch of sea or Himalayan salt to water, especially during extended fasts, to restore vital electrolytes like sodium and prevent headaches and fatigue.
Flavor with Fresh Ingredients: Infuse water with fresh lemon, lime, ginger, mint, or cucumber slices for a zero-calorie flavor boost, but avoid chewing solids.
Consider Apple Cider Vinegar: Diluted ACV can help curb appetite and stabilize blood sugar during a fast, but ensure it's heavily diluted to protect tooth enamel.
Avoid Sugary and Calorie-Rich Additives: Steer clear of all sugar, honey, and high-calorie liquids like juices, protein powders, and sweetened drinks, which will break your fast.
Choose Unsweetened Alternatives: Opt for plain sparkling water, black coffee, or unsweetened herbal tea for variety, as they are generally accepted during fasting.
Be Mindful of Supplements: Only take calorie-free, water-soluble supplements during a fast; fat-soluble vitamins (A, D, E, K) require food for proper absorption and should be saved for your eating window.

Why Hydration is Crucial During a Fast

During fasting, your body continues to lose fluids and essential minerals, known as electrolytes, through urine and sweat. When you stop consuming food, your insulin levels drop, which signals the kidneys to excrete more sodium and water. This rapid loss can lead to symptoms commonly referred to as the 'keto flu,' including headaches, fatigue, muscle cramps, and brain fog. Proper hydration goes beyond simply drinking water; it's about maintaining the right balance of fluids and electrolytes to support nerve and muscle function, regulate blood pressure, and sustain energy levels. Supplementing with the right additions to your water can help mitigate these side effects and make your fast more comfortable and sustainable.

Safe Additions to Water During Fasting

Electrolytes (Salt)

Adding a pinch of unrefined salt, such as pink Himalayan or sea salt, to your water is one of the most effective ways to replenish lost electrolytes during a fast. Sodium is a crucial electrolyte for maintaining fluid balance, and a deficit can cause significant discomfort. For fasts longer than 12 hours, many people benefit from a pinch of salt in the morning to prevent headaches and dizziness. For longer or more active fasts, an unflavored electrolyte powder (free of sugar or artificial sweeteners) can provide a more comprehensive mineral profile, including potassium and magnesium.

Lemon or Lime Slices

A small amount of fresh lemon or lime juice provides flavor with minimal calories, making it safe for most fasting protocols. A squeeze from a quarter of a lemon typically contains only a couple of calories and won't significantly impact insulin levels. Besides flavor, the citrus can offer a boost of vitamin C and antioxidants. Always opt for fresh juice over bottled varieties, which often contain added sugars and preservatives that will break your fast.

Apple Cider Vinegar (ACV)

Diluted apple cider vinegar is a popular addition during fasting, with some evidence suggesting it can help curb appetite and stabilize blood sugar. Mix one to two tablespoons in a large glass of water to minimize its acidity and protect your tooth enamel. This potent drink can aid in controlling cravings, which is especially helpful during longer fasts.

Fresh Herbs and Cucumber

For a no-calorie flavor infusion, fresh herbs like mint, basil, and rosemary, or thin slices of cucumber, are excellent choices. This adds a refreshing taste without any caloric impact. Just be sure not to chew the cucumber slices, as this can stimulate digestion and potentially break your fast, depending on your goals.

Unflavored Sparkling Water

If you find yourself missing carbonated beverages, plain or unflavored sparkling water is a perfect substitute. It provides the satisfying fizz you crave without any calories, sugars, or artificial sweeteners that would disrupt your fast. Always check the nutrition label, as some flavored sparkling waters may contain hidden additives.

What to Avoid in Your Fasting Water

Sweetened Beverages and Artificial Sweeteners

Any drink containing sugar, honey, or artificial sweeteners should be avoided. These can spike your insulin levels, completely negating the benefits of your fast. Even 'zero-calorie' diet sodas with artificial sweeteners like sucralose or aspartame can trigger a cephalic-phase insulin response in some people, so it's best to stick with truly zero-calorie, natural options. This also applies to flavored water enhancers like MiO that contain these sweeteners.

Calorie-Containing Supplements

Most vitamins and supplements that contain calories, protein, or fat should be saved for your eating window. For example, collagen powders, branched-chain amino acids (BCAAs), and protein powders all contain calories and will break your fast. Additionally, fat-soluble vitamins (A, D, E, and K) are best absorbed with a meal containing fat, so they are not ideal for consumption during a fasting period.

Fasting Water Additions: Safe vs. Unsafe


Item	Safe for Most Fasts?	Reason
Pinch of Salt (Sea or Himalayan)	Yes	Replenishes electrolytes without calories; helps prevent 'keto flu'.
Fresh Lemon/Lime Slices	Yes	Adds flavor and antioxidants with minimal calories; avoid sweetened juices.
Apple Cider Vinegar (ACV)	Yes	Can curb appetite and stabilize blood sugar when diluted; low calories.
Fresh Herbs (Mint, Ginger, Cucumber)	Yes	Provides calorie-free flavor infusion; do not chew solids.
Plain Sparkling Water	Yes	Offers a satisfying fizz without sugar or calories.
Sugary Lemonade/Juice	No	Contains calories and sugar, which spikes insulin and breaks the fast.
Protein/Collagen Powder	No	Contains calories and protein, which triggers an insulin response.
Gummy Vitamins	No	Contain added sugars and calories that break the fast.
Diet Soda with Artificial Sweeteners	Consider 'No'	May trigger an insulin response in some people; best to avoid.
Bone Broth	Consider 'No'	Contains minimal protein and calories, but purists and those fasting for autophagy will avoid.

Conclusion: Strategic Hydration for a Successful Fast

What you put in your water when fasting can significantly influence your comfort and the overall success of your fasting protocol. For most fasters, the goal is to consume only zero-calorie, non-insulin-stimulating beverages. Strategic additions like a pinch of salt for electrolytes, a squeeze of fresh lemon for flavor, or diluted apple cider vinegar for appetite control can be invaluable tools to help you manage your fast effectively. However, it's equally important to be mindful of what you should avoid, including all forms of sugar and calorie-containing supplements. By making smart choices about your hydration, you can support your body, minimize unpleasant side effects, and more easily achieve your fasting goals. As always, listen to your body and consult a healthcare professional, especially for extended fasts or if you have underlying health conditions.

For additional resources on fasting and diet, consider consulting authoritative health websites like Healthline.

Frequently Asked Questions

Yes, adding a small amount of fresh lemon or lime juice to your water is generally safe for fasting. It provides flavor and antioxidants with minimal calories and won't disrupt your insulin levels significantly. Avoid using bottled juices with added sugars.

No, a pinch of salt does not break a fast from a caloric standpoint. Salt contains no calories and doesn't trigger an insulin response. In fact, it's encouraged during longer fasts to help replenish electrolytes and prevent symptoms like headaches and muscle cramps.

Plain or unsweetened sparkling water is perfectly fine to drink while fasting. It has no calories or sugar. However, check the label of flavored sparkling water to ensure there are no hidden sweeteners that could break your fast.

Yes, many fasters use diluted apple cider vinegar. Mix one to two tablespoons in a glass of water. It is known to help curb appetite and is low in calories, but should be used in moderation.

Zero-calorie, unflavored electrolyte supplements are fine during a fast, but avoid supplements with calories, sugar, or protein. BCAAs and collagen powders contain protein and will break your fast.

While technically zero-calorie, artificial sweeteners may trigger a small insulin response in some individuals, potentially interfering with fasting benefits. It's best to stick to truly zero-calorie natural additions to be safe.

Symptoms like headaches, dizziness, fatigue, muscle cramps, and lightheadedness can indicate an electrolyte imbalance. Adding a pinch of salt to your water can help alleviate these symptoms.