All kombucha has a bit of alcohol in it due to the sugar fermenting with the yeast. Commercial brands that have less than 0.5% by volume in it can be sold as “non-alcoholic.” Any more than that and the government considers it to be booze. Fermentation time, temperature, and the way the drink is stored all play roles in how strong it becomes. Some kombucha continues to ferment even in the bottle
Some reports link the homemade variety to stomachaches, dizziness, nausea, infections, and allergic reactions. The risk is high when people brew it in unclean conditions. That makes it easy to taint during fermentation. Brewing or storing it in glazed ceramic pots has a link to lead poisoning, too.
Stay away from this drink if you have a weakened immune system or a long-term health condition -- especially liver, kidney, or lung disease. Don’t drink it if you’re pregnant. It’s not for young children either. But if you’re a healthy adult, the store-bought kind that’s pasteurized is fine in moderation -- but not more than 12 ounces per day. Read the nutrition label, though, because the sugar and calories can vary quite a bit by brand.
It’s important to always keep kombucha in the refrigerator, even before you drink it. If you leave a capped bottle at room temperature for a while, the carbonation in it could build up -- and you might get a surprise splash when you open the bottle. The cold of the fridge also slows the fermentation.