I found both dark and light rye bread at the store but it was the factory-made kind. I definitely made mistakes with both batches including adding way too much bread to the light kvass.the bottles need a day to carbonate then we shall see how well they turned out. Not that I have any reference for the flavor.
So I only fermented for ~a week and I sort of combined a few recipes I found online including one from a YouTube channel called TheBruSho. Here is what I came up with after reading a few:
Rye Kvass:
~7 Pieces of Rye Bread(preferably dark or Russian rye)
~1/2 gal [1.9L] Water
~2/3 cup [150g| sugar(can be substituted with wort, honey, molasses, ect)
Handful of raisins or any other dried berry (cut in half if you like) ~10
Optional: Pinch of bread yeast or tea sppon of sour dough starter to accelerate the fermentation
Toast the bread so dark as to be almost burned
Boil enough water to cover the toast and pour over toasted bread pieces
Wait until room temp and add raisins and sugar
Ferment 3-5 days depending on your fermentation activity. Bottle with more raisins and a tea spoon of sugar and set on counter 2-3 days Refrigerate and drink
Sourdough starter would probably be a superior option - lactic acid fermentation is essential for a good kvass
I used sour dough starter on my second attempt and it carbonated way faster than just raisins.
Totally believable