Why am i craving grapes?

hi i been dieting and going to the gym, but over the last few days i been really craving grapes really badly and keep full filling this craving with eating a lot more grapes than i normally do - im pretty positive i am not pregnant as i have not done anything recently to get pregnant (unless i sat on a sperm infested public toilet seat recently at a club i went to lol), but what could be causing this craving?