Barely Fermented Apple-Grape Juice

My brother-in-law makes this for me since I am allergic to wine and beer. It's one percent alcohol and even less when diluted. Take a quarter of a cup of apple grape juice and warm it to wrist temps. Dissolve a half teaspoon of Fleishmann's active dry yeast. When proofed add a quart of juice. Close in a plastic empty seltzer bottle. Don't over fill it. Allow an inch of head room. Let the bottle sit at room temps for 24 hours, or if your house is 50 degrees, place it in a 70 degree spot. Check on it, release air as needed. Pressure builds fast! Refrigerate and enjoy when cold. It will be bubbly. It's very sweet, dilute with three parts plain seltzer.
Next time you make it use the cultured leftovers rather than yeast, to cultivate your next batch. Your colony of yeast will become specialized and adapted to your home-kitchen environment.