One of the most common questions I get from coaching clients is, "What can I actually drink during my fast?"

The short answer is water, black coffee, plain tea, and electrolytes.

The longer answer is where things get interesting, because not all drinks are created equal, and some of the stuff marketed as "fasting-friendly" will absolutely compromise your results. Let me break it down.

Water (Yes, Obviously)

This one's straightforward. Water is your foundation, and you should be drinking plenty of it during your fast. 

But here's what most people miss: when you fast, your kidneys flush sodium faster than normal. That's why you might feel lightheaded or foggy or get headaches a few hours in. It's not hunger. It's dehydration and electrolyte loss.

Water alone won't fix that. You need to replace what you're losing, which brings us to electrolytes.

Black Coffee

Black coffee is fine. It has no calories, no sugar, and doesn't trigger an insulin spike.

Some research even suggests caffeine can enhance fat oxidation during a fast, so if you need your morning coffee, you're good to go.

The key word here is black. The second you add cream, milk, sugar, or one of those flavored creamers, you've broken your fast. That goes for bulletproof coffee too. MCT oil and butter have calories, and they will break your fast.

Plain Tea

Green tea, black tea, and herbal tea work just fine. The same rules apply as with coffee: nothing added.

Green tea is particularly good during fasting because it contains L-theanine, which promotes calm focus without the jitters you might get from coffee.

Electrolytes

This is where most people run into problems.

You need electrolytes during a fast. Sodium, potassium, and magnesium. When insulin drops, your kidneys excrete more sodium, and you lose the other electrolytes along with it. That's why you feel terrible during fasts. It's not a willpower issue; it's physiology.

The problem is that most electrolyte supplements are loaded with stuff that will compromise your fast.

Stevia, for example. Research suggests it can still trigger an insulin response in some people. Maltodextrin is basically sugar in disguise. And "natural flavors" is a catch-all term that can include hundreds of lab-processed compounds. More on that in another post.

So yes, drink electrolytes. But read the label first. If there's a long list of "other ingredients," you might want to find something cleaner.

What to Avoid

Anything with calories breaks your fast. That includes juice (yes, even "fresh-pressed"), milk or cream, smoothies, bone broth (great food, but not for fasting), cacao, diet sodas (zero calories, but the artificial sweeteners can affect gut health and cravings), and additive-filled coffee.

If someone tells you bone broth or bulletproof coffee "doesn't count," they're wrong. Calories are calories. If the goal is metabolic rest, those things interrupt it. Most store-bought coffee alternatives will break your fast, unfortunately.

The Bottom Line

Keep it simple: water (lots of it), black coffee if you need it, plain tea if you prefer, and clean electrolytes to replace what your body loses.

That's it. You don't need fancy fasting drinks or special supplements with 15 ingredients. You need hydration, electrolytes, and the discipline to keep it clean.

If you're looking for an electrolyte that won't compromise your fast, I built Optimize for exactly this reason. It contains zero calories, zero sweeteners, and zero "natural flavors." Just electrolytes and functional ingredients that actually support your fast. Other ingredients: none.

I sincerely hope it helps you fuel your fast.

— Schuyler