Adapted from a recipe that someone posted on the GAPS yahoo group.
Beet Kvass
1/2 c starter (either juice from last batch, or whey, or sauerkraut juice), optional
1 med beet, peeled and roughly chopped
1 tbsp. salt
5 cloves garlic, peeled and crushed
1 head (or so) cabbage, roughly chopped (big hunks)
Wash beet pieces, and put them into a one-gallon jar. Add the garlic, and then cabbage chunks until the jar is full. Add salt, and fill with water to within one inch of the top (make sure veggies are submerged).
Cover the top with a large cabbage leaf, fill jar with water, and cover tightly. Leave anywhere from 5 days to 1 month, the longer the better, on the counter or in the pantry. Add water if the liquid level gets too low.
When done, strain juice into a jar and refrigerate. You can then add another tablespoon of salt and refill with water for a second, weaker batch. When that batch is done you can either eat or compost the veggies.