I made a batch in June that was 3.75 gal of Apple juice and 2.25 gal of Welch's Concord Grape. OG was 1.058, giving 7.75% ABV. I sweetened it with four cans of frozen grape juice concentrate. Tasted like a sparkling grape wine.
I made it because that was all the apple juice Walmart had at the time and thought 'Let's see what this would be like.' Meh, I won't be repeating it.