This works better if you are a master of alchemy, but works any way. Fast travel to Skingrad, pick all the grapes, then make them into a potion of restore fatigue.
If you are in the Mages Guild and you have it good with the merchant you can sell it for 20 gold.
You should haggle w/ them first. Then you should have about 1 thousand to 2 thousand gold after you sell.
It works just as well as any other ingredient, plus the other normal foods will be in the same spot as the grape potions.
It can also work better if you go to the Guilded Carafe, the merchant there has more money.