It is generally advised to break a fast with fresh juice, because this is easiest on the digestive system, which has been out of work for some time. This could be orange juice, grapefruit juice, tomato juice, grape juice... The second day, you can eat whole fruits and then after that move on to other foods. I have never heard or read of grapes being any different from other fruits in this respect.

This is for longer fasts. If you have only fasted for a couple of days, then you can immediately go back to normal meals. Also, note that many people (including myself) have broken longer fasts (of several weeks) with a normal meal, without having had any problems. But it's better to be on the safe side, as some others that have tried this have had severe indigestion or other stomach problems.