How do I make my bunny to eat hay?

I have a 6 year old bunny, and he has an extended lower jaw (sorry, English isn’t my first language and I don’t know how to better explain it), that causes his teeth to grow without any grinding the vet says is a genetic, second, we have to cut them every one and a half month approximately, the vet has told us to stop feeding him so much pellet and give him hay or any other grass to chew. But my bunny doesn’t want to eat hay, he just pushes the plate with hay off and it ends up scattered all over his cage. We buy him hay with some apple flavour or something like that and he doesn’t even try it. We are giving him less pellet because the vet said he was a bit chubby.

Note. Any game or enrichment activity would be nice too, since he’s mostly free to go around our flat we are open to mostly anything.