My son is rather fond of a fermented tea concoction called Kombucha. He buys it commercially, and he has also made it himself. I've never tried it.

I don't think the commercial variety has any appreciable amount of alcohol. I think they keep it under 0.5% so it won't be classified as an alcoholic beverage. Wikipedia says it can be up to 1.5% which is still a lot less than beer.