Lightly alcoholic (< 1%) when store-bought, but mind you, we often stored it at room temperature - which I estimate, over a few days / weeks got the alcohol content up to 3-4 percent. I used to guzzle this stuff as a kid, heh. Still do!
Always make with rye bread - versions can be made with regular, white bread, but it's not the same. If rye bread is unavailable in sufficient quantities, a 50/50 mix or rye to white bread is permitted.
From my youth, I recall the large, handsome wheeled wagons (container trailers, almost), full of fresh kvass, that would typically be parked at venues. Particularly fondly do I remember one that was a frequent sight at the VDNKH in Moscow. It was there, I believe, that I'd first tried the beverage, at an age no older than four or five.
A great advantage of kvass is that it's ready to drink within a few days. Admittedly, I seldom brew my own anymore; as I am often in the local Eastern European grocery store, I tend to purchase off-the-shelf varieties. Nonetheless, I thought a recipe may yet be of use to those interested:
A very healthy probiotic snack. Unlike Western, vinegar-based pickles, these are salted, and then lacto-fermented. Think sauerkraut, but with cucumbers. When I first came to the West, I fell in love with vinegar-pickled products, but as the years pile on, I find myself reaching for the kind I'd grown up with more and more often.
Production is very different from Western pickles, although, these are less shelf-stable. Canning isn't required, which is a bonus; I never took up canning out of fear of botulism. Perhaps an unfounded one, but one I have had for years nonetheless.
Another classic dish, Georgian-style pickled cabbage. When I was a boy, my father told me many stories of his childhood in Sukhumi, and of the many adventures and misadventures he'd gotten himself into. People, at the time, were assumed to make most of their foods themselves - this, of course, includes pickles, and such other goods.
One such story revolved around him (no older than 7) stealing pickles from the incredibly large, buried clay pots, where enormous batches of all manners of delicious and crunchy treats were kept - everything from the aforementioned cabbage, to garlic, to tomatoes, and pretty much any other vegetable you can imagine.
The red cabbage was a common side-dish (practically a condiment) to nearly every meal I've had growing up - whether it be mamaliga (a sort of porridge made with corn millings) or lobio (a delicious bean stew), the crispy, salty cabbage was a wonderful palate cleanser to take between bites. Believed to greatly improve digestion, this was a product commonly found in many kitchens around the country.