The largest beverage company in China and therefore one of the largest in the world is the ridiculously named 娃哈哈 (wá hā hā, literally 'baby haha'), founded in 1987 by Zong Qinghou (宗庆后) with three employees and a $20,000 USD loan (140,000元).
They sell everything drinkable except hard liquor and now have around 30,000 employees. Their top seller is their purified water which I often buy.
I was surprised to see today that they have launched their own kvass, which they call 格瓦斯 (gé wǎ sī) in an attempt to replicate the Russian квас phonetically.
Unfortunately, the literal meaning of 格瓦斯 is 'standard gas', wǎ sī being an earlier attempt to replicate 'gas'. A linguistic mess.
Apart from the wort*, which they don't give details of, it contains apple juice and 'grape syrup', sugar and a bunch of chemicals with long names, none of them necessary.
What does it taste like? How the heck would I know? I lived in Russia in the latter years of the Soviet Union, where I drank it once and found it disgusting. Never again.
* "A sweet liquid produced by steeping ground malt or other grain in hot water, which is then fermented to produce beer."