Hi Roei_ny, I think there's not much you can do. I have a brother who is just that age (just had his bar mitzvah) and he is just like that. Doesn't like any fruits or vegtables. My mother has learned (through me basically) that we learn on our own.. and now when his acne is starting to appear we are all persuading him to eat better and to drink water instead of coke. It takes time, but it does work, and I am the living proof.