Can kvass be made without bread?
Kvass can be made without bread, e.g. "beet kvass" can be gotten going with minced raw beet root (fill jar between 1/4 and 1/3 full), a 3% saline solution (or thereabouts?), and a dollop of sourdough starter. I believe other starters (e.g. from milk products) can also be used, but I haven't dabbled with those. Mine bubbles for two to possibly three days, though mold may be a problem, so you'll want to monitor for that, figure out a reasonable upper limit, and strain and consume or find a refrigerator somewhere to stash the kvass in.

Fresh ginger root also makes for a nice addition, or spices to taste, or carrots...