If your homemade kombucha isn't fizzy, it's because there isn't enough carbonation in it. This can occur for a number of reasons, but there are a few common mistakes. One, you're not not fermenting it long enough, especially during the second fermentation period. Not using fermentation grade bottles is another common reason, as is leaving your booch to ferment in too cold of an environment (lower than 68 to 78 degrees F).