Hi Jess and welcome.
I have never been able to find apples that aren't starchy so I have been afraid to try the apple fast. But you can use something else to fast on. The idea is to use just one food to give your gut a break so something like green grapes are good to fast on if that would be easier on your GI tract. I have also done a cherry fast when they were in season, and even cucumbers.
Good luck with the diet.
Annette