Some wines use partially raisined grapes to make a very sweet flavor profile, like [Sauternes.](https://en.wikipedia.org/wiki/Sauternes_(wine\))
When I read the link, I immediately said to myself “Well, I guess it’s just like prune juice.” But that still doesn’t mean it doesn’t seem strange on paper.
And my understanding is that Amarone wines also let the grapes dry out a little to concentrate the flavors. Not raisined, but just a bit shriveled. I love Amarones.
Commandaria is another famous, and ancient, sweet wine made with dried grapes
The concept of raisin juice might seem a bit odd, since raisins are, after all, dried grapes, and grape juice is an already well known substance. However, raisin juice is not the same thing as grape juice. Because raisins are dehydrated, their juice is in turn a highly concentrated substance, with less water than grape juice. It is also intensely sweet, as typically sweet varieties of grapes are used to make raisins, and their sugar content increases with dehydration
For those who can’t tell if this is a joke or not
Absolutely not a joke! I was eating some granola bar and noticed in the ingredient list. I thought it was some ridiculous labeling thing and had to look it up. The bit you quoted was what I figured it was, but it still sounds absurd on the surface.
Might be real, but it’s still a joke. Grape juice concentrate.