You're 14 hours into a fast. Your stomach is making decisions your brain hasn't approved yet. You reach for a cold brew from the fridge and then pause — does this break my fast?
Short answer: it depends on which protocol you follow and how strictly you read it. Plain black cold brew is very low in calories and contains no sugar, and many fasting protocols allow it — but whether it fits yours is your call, and worth running past your doctor if you are fasting for a medical reason. Here's where it gets complicated — most canned cold brews aren't just coffee and water.
Black Cold Brew and Fasting Protocols
Intermittent fasting works by keeping insulin low long enough for your body to shift from burning glucose to burning stored fat. That metabolic switch happens when you avoid caloric intake that triggers an insulin response.
Plain black coffee — including cold brew — is very low in calories, though the exact number varies by brand. Bare Brew is 20 calories per 12oz can with zero sugar. Whether a drink at that level counts as breaking a fast depends entirely on the protocol you follow: some allow any near-zero-calorie, zero-sugar drink, others allow water only.
Cold brew does differ from hot coffee on one measurable point: cold brewing extracts fewer of the acids that hot brewing pulls from the same beans — research published in Scientific Reports found cold brew has a lower total titratable acidity than hot brew, though pH is comparable. That is a property of the brewing method, not a promise about how coffee will sit on an empty stomach. If you have a digestive condition, talk to your doctor.
What Breaks the Fast (That People Add to Cold Brew)
The cold brew itself isn't usually the issue. It's what people put in it. Cream, milk, oat milk, sugar, flavored syrups — all of them add real calories, and most protocols count them as ending the fast. Sugar and milk sugars also drive a blood sugar and insulin response. Even "sugar-free" sweeteners are debated. Some studies suggest artificial sweeteners can trigger a cephalic-phase insulin response — your body starts producing insulin just from tasting sweetness, even without actual sugar.
The simplest move during a fast: drink your cold brew black. Zero sugar. Zero cream. Zero "natural flavors" that might contain trace calories or sweeteners.
The Hidden Problem With Most Canned Cold Brew
Check the label on most canned cold brews. You'll find several ingredients beyond coffee and water. Potassium bicarbonate. Ascorbic acid. "Natural flavors." Each one is a question mark for fasting purists.
If your cold brew has two ingredients — coffee and water — there is nothing to decode. Bare Brew is exactly that: Honduran Arabica cold brew and filtered water. 320mg of caffeine. Zero sugar. Zero additives.
At 20 calories per can with zero sugar, it is about as plain as a canned coffee gets. Whether that fits your fasting protocol is up to you — if you are fasting under medical supervision, ask your doctor first. Either way you get the caffeine and the focus.
When to Drink Cold Brew During Your Fast
Timing matters. Caffeine hits peak blood concentration about 30-60 minutes after consumption. For most 16:8 fasters, the sweet spot is mid-morning — around 9-10am if your eating window starts at noon. That spreads the caffeine across the longest stretch of the fast.
At 320mg per can, one Bare Brew covers your entire fasting window. You don't need a second coffee. You don't need to wonder whether cup number three is pushing you past the 400mg daily FDA guideline. One can. Done.
Bottom Line
What ends a fast for most people is the stuff added to the coffee — or the stuff brands put on the label. Whether plain black cold brew fits your fast depends on the protocol you follow, and that is a decision to make with your doctor if you are fasting for medical reasons. Keep your cold brew clean, keep it black, and read the label.
