My 5 yr old wont eat!!!

QUEEN

I've tried everything I've gone to doctor specialist everything in my son just does not like to eat. The doctor does not want to put them on PediaSure because she says she does not want him to get used to drinking that understand but the same time he needs something. The only thing he will eat is peanut butter and jellies and sometimes chicken nuggets and sometimes mac and cheese. That is literally it. the only healthy thing that he will eat is fruit. That is it does anybody have any suggestions of some food that I could give to a picky eater and I need a really picky eater. The doctors don't know what else to tell me so I figured maybe some ladies on here have some good advice.