
Give him a choice - take it or leave it!!! Sounds hard, but if you pander to him now, you'll spend your time trying him out with different things which he'll eat for a few days then demand a change. Feed him at his usual times (once or twice a day) & if he doesn't eat his food within about 15 minutes, take it up & don't feed him until his next meal time. Stick to it (and don't give him anything in between) & eventually he'll be hungry enough to eat what's put in front of him. Not easy, when you're worrying about him not eating but he won't starve himself to death - he's just trying to get his own way with you!
(I take it that other than not eating, he's fit & healthy - if not have a vet check up)