How can i use an exercise app to prevent cravings?

Not sure: Your question is not very clear. Craving for what? Food exercise, etc? Usually cravings are caused by repeated use of a substance, i.E caffeine, chocolate, etc; your body gets used to this; the best thing is to wean yourself off. You can go cold turkey or slow wean. Drink water because most things are dehydrating, chart to see triggers: menstrual cycle, moods, weather etc to prepare yourself.