You May Call Them Raisins
I don't know why. Well, I do know that the sweetness concentrates itself as the skin shrinks. That's my scientific explanation.
Put 'em in salads, especially arugula, feta, walnuts, pears . . . or whatever.
This is also a way to use up grapes that are getting a little old. Soft. (A natural consequence I'm told.) Not quite moldy (just throw those out, you lost the opportunity).
Here's how hard this is: put green or red seedless (duh) grapes on a cookie sheet you don't care about (you know, the one you've never really gotten clean and just gave up on it early), put grape-seed oil on them, roll them around in it, bake for oh, eight, ten, hours at around 200 degrees. You might be able to speed up this process at a higher temperature but I've not tried that. When they look done to you, briefly let them visit a paper towel on both sides to soak up some of that oil. Refrigerate. Use as desired.