I know that blue grapes (they must have seeds) are full of antioxidiants and cleans the body wonderful.
I found the following link from google.com and searching for grapes fasting. I do it myself regularly and it is just great.
In Russia, there is a sanitarium in Yalta that specializes exclusively in the grape fast. Patients begin by eating 1 pound of fresh raw grapes and work up to 10 pounds per day.
Besides detoxifying the entire body and curing gesture-intestinal ailments, the grape cure greatly enhances metabolism and strengthens the heart muscles. Some patients in America have credited the grape with curing otherwise 'incurable' cancers." (quote end)