How to re-carbonate flat kombucha
At room temperature, the live yeasts in your brew eat sugar and convert it into carbon dioxide. That's true in the vessel, in the bottle — and even in a bottle you've already chilled or opened.
Kombucha Tip: Re-carbonating your opened kombucha · Watch on YouTube
Fermentation happens in your brewing vessel during F1 and in the bottle during F2 — but here's the underused part: even after refrigeration sends the yeasts dormant, a few hours back at room temperature reactivates them. As long as the bottle is sealed airtight, they'll start eating sugars again and producing CO₂. It'll get fizzier.
Two scenarios where this saves the day
- The batch chilled too early. You refrigerated after 3 days of F2, popped one open, and it's not as fizzy as you'd like. No worries — take the rest of the batch out of the fridge and give it another day or two at room temperature to bump up the carbonation. Just re-chill before opening: cold liquid holds fizz in the drink (and off your ceiling).
- The half-finished bottle. Opened a bottle and didn't finish it? Seal it back up and leave it out for at least a few hours — it'll regain some of that lost carbonation. It may come back slightly less sweet (the yeasties ate sugar to make that CO₂), but hey, it beats flat kombucha.
This really only works for homemade kombucha. Store-bought brands may use yeast inhibitors or other tricks to halt fermentation in the bottle — labels can say "raw" without the FDA checking — so depending on the brand, a flat store-bought bottle may stay flat forever.