Prunes and grapefruit are two different fruits, although they both have the word "Xi". Prunes are purple plums, which are sweet and rich in vitamins and minerals. On the other hand, grapefruit is a kind of citrus fruit, which tastes sweet and sour and is rich in vitamin C and antioxidants.
As for "burning prune grapefruit juice", I'm not sure if it's genuine. Please choose formal channels to buy goods, and pay attention to verify the brand, production date, shelf life and other information of the goods.