Unsweetened grape juice is an interesting concept. It’s a bit like calling for unsweetened orange juice or unsweetened cane syrup.
To put it another way, eight fluid ounces of unsweetened grape juice has the same amount of sugar as eight Oreo cookies. (To be fair, Oreos have more calories, because they have other ingredients.)
To put it a third way, one of the most common forms of “sweetener” added to other fruit juices is grape juice. (“100% Real Juice!” Well, Soylent Green was 100% real meat.)
The likely reason for the distinction is that, when frozen concentrated juices were new, the most common kind of frozen grape juice concentrate included some form of sweetening. If you look at the labels of these grape juice “cocktails,” however, the reconstituted beverage turns out to be slightly lower in sugar per serving than “unsweetened” grape juice.
That’s true whether the added sweetener is grape juice concentrate, corn syrup, or high fructose corn syrup, so it’s not to say you wouldn’t rather have the higher sugar option. It’s just to point out the weirdness of calling grape juice unsweetened.
From a box sold in Chicago, Illinois.
1/3 cup pineapple juice
1/2 cup unsweetened grape juice, or raw beaten grapes in liquefier
Few drops of lemon juice