So far, I have tried a number of commercially made brands of kvass, one of them is even a winner of taste and flavor testing competition recently held in Russia. Unfortunately, they do not compare to the beloved kvass we all remember sold during Soviet days, nor do they taste near as good as homemade kvass.
In order to provide a longer shelf life as well as extended warehouse storage, these companies have to cut corners, which includes artificial carbonation, sweeteners, flavoring, and coloring, sadly ruining the taste. But more importantly, naturally made kvass is full of nutritious qualities which lack in commercial brands. Those qualities are achieved during the fermentation process, which is either completely cut out during commercial production or its time is so short that it really makes no difference.
Kolokol Kvass's flavor and color is derived from oven roasted dark rye bread. Its carbonation comes from being naturally fermented at room temperature. It is then cured and filtered while being held in the cooler for 5 days. Finally, it is bottled and stored at cool temperatures for freshness. We are not cutting any corners. Kolokol Kvass speaks for itself.