I don't know if anyone actually sells a supplement identical to the dehydrated fruit juice you are describing. But I wouldn't be surprised if someone was trying to sell something similar, and I would be even less surprised if they were succeeding and making a profit from it.

I suppose it is a little unfair to say that such a supplement would do nothing at all. But it wouldn't be a realistic alternative to eating fruit, because much of the nutritional content of whatever fruit it was made from would be lost due to the dehydration process. Which would render such a supplement more or less useless. Even fresh fruit juice is far less healthy than eating the actual fruit it is made from, because nearly all of the dietary fibre is excluded and some of the vitamins and minerals are lost.

Also, provided that the person taking said supplements had a reasonably varied and balanced diet in the first place, they wouldn't really need to supplement their diet with anything. A dried fruit extract wouldn't be of much (if any) benefit.

The "nutritional supplement" industry in the USA is basically a joke. It's more or less completely unregulated - you really can get away with making any claim you like on the label. Not so much in Europe, where supplement manufacturers now have to legally provide the same clinical evidence for stated claims as any drug manufacturer does.

In the USA though, anything goes. If you are a supplement manufacturer, you can contaminate your products with just about anything you like. Your product doesn't even have to contain what it says on the label. Neither the Federal Trade Commission or the Food & Drug Administration can come after you, unless what you are selling actually makes people sick.