I usually make this kvass after making Abigail's Applesauce: a family favorite. We then make use of the apple peelings and cores to make a delicious probiotic beverage. Waste not, want not!
Fill a quart jar 1/4-1/3 full of apple peelings and cores. Mix enough of a solution of the following cover the apple scraps:
1. Place a lid on the top of the jar and turn back slightly so it's not tight, allowing the pressure to escape.
2. Culture on the counter for about 2 days in the summer and 3 days in the winter.
3. Strain scraps from the liquid and store covered in the fridge.