It's no secret that kombucha contains alcohol. Albeit usually in trace amounts that the body is able to metabolize quickly, and you are none the wiser. People will say to me, even after drinking a 1 oz. sample at a market, that they've received a "buzz" from my kombucha, insisting that I'm trying to get them drunk. It's definitely not from alcohol.
I find it hard to believe that any beverage artisan wants consumers to feel anything but fulfilled from drinking their product. Not to suppose that inebriation forfeits assessment of flavor (though we can all see how this can be possible in extreme circumstances), but getting hammered on a fine microbrew or expensive bottle of wine to an extent cheapens its value as a thing carefully-sourced and produced. Nuances and layers of flavor are best appreciated in careful consideration, and on the whole I'd say the ability to ascertain subtleties towards the end of a sizable run of alcohol consumption becomes difficult, possibly only overcome through diligent practice and variation (during the session) in the type/style of beer, wine, etc. Perhaps differences in many varieties, during a stint at a wine or beer festival, become relative to each other, making discrimination easier.
I'll state for the record that I've never become drunk on kombucha; if anything, after a long day of working at the market selling kombucha, and the requisite consumption of it that accompanies the event, I feel energized and content, with acute senses, perception and mobility that would assist me in anything from writing a research paper to driving across the country. I won't encourage anyone to drink that much kombucha (sometimes up to a gallon a day), but I'm definitely an aberrance in the field; not because I think kombucha is bad for you, but because I believe (and don't always practice) the "less is more" and "everything in moderation" approaches to consumption. Maybe 32 oz. a day feels good for you, maybe 4 oz. feels right. Maybe I want 2 liters.
That Being Said
You can make kombucha that contains a sizable amount of alcohol, akin to that of a standard American lager, and perhaps more (do experiment, please).
There are definitely kombucha companies out there who have chosen not to control the amount of alcohol in their kombucha, and they should be commended, be it for better or for worse.
There are also companies that have produced hybrids of kombucha and beer, with results ranging from 5-10% alcohol by volume. Whoa! Experimentation is the spice of life, and I'm happy these boundaries have been pushed.
However - I would be hard-pressed to say that I've completely enjoyed any of the marketed high-alcohol kombuchas available. Obvious merits are in the realm of a sour beer, of which I do count myself a fan, but something really different happens in kombucha - kombucha contains bacteria; beer excludes all but a certain strain of yeast (that's why extreme sanitation and an airlock are used during the production of beers).
The only way I've found to make palatable and delicious (appreciably) alcoholic kombucha is in brewing kombucha wine; I've achieved about 5.5% alcohol, with only a few caveats in flavor based on a few different factors.
In upcoming posts, I'll describe my process of making kombucha wine, complete with suggestions and recipes - in the meantime, do some experimentation yourself! Don't wait for me to spell it out. I'll give you a hint - airlock, champagne yeast. Go!