A few years back, one of my kids put me on to a youtuber called Life of Boris, who (amongst other things) makes slavic foods in a fairly chaotic way.
One that piqued my interest was kvass, a slightly fermented rye bread drink. His recipe is straightforward and easy-to-understand.
I've been making this for a while now, using my still as a heater together with an InkBird temperature controller to keep everything at 33°.
It comes out as a slightly tart, slightly sweet fizz that is murky, but very refreshing.


Unlike with beer, which is an anaerobic ferment, this is an aerobic ferment that needs air, and it produces a lactic tang almost like sour cream. Boris' comment that it is partway between a cider and a light beer in taste is pretty accurate. 
It has the annoying tendency to foam all over the place when opened, so I've learned to slowly open the cap and let pressure release over a few minutes. 
It is wonderful after a hot day of working outside but when you don't feel like having a beer. With less than 1% alcohol, it's fine for the kids as well. 


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