When you say he then goes back to doing nothing, would it work if you keep reminding him? In my case, believe it or not, nagging did work… (My son, at his age right now, keeps “forgetting” a lot of things – not that he doesn’t know but I believe there’s just so many things distracting them these days).
On things that my son is “uncomfortable” doing, we literally force him out of his comfort zone eg. artichokes, trying soda, etc. He is 13 and is unusual in that he is in his super comfort zone and would not want much to “move it” eg try new things, eat at new restaurants etc 
hope a little bit of nudging/nagging works… (at least on lacrosse games etc - the lighter ones)