How unhealthy are Apples to Veiled Chams?

I am curious if apples are dangerous in small amounts to chameleons. I read a few days ago that somebody mentioned that apples are not a good diet for them to add since they contain fruit acid (idk the english name) and that they should not eat them on a daily basis.

Currently he eats two bites a week an he reaaaaly LOVES them. The rest of his diet are of course crickets and locusts which he eats on a 2 day basis.
It would be a shame to cut that off but I want a healthy diet for him.

If apples are too unhealthy should I try Cucumbers? Can i feed them too but more frequent?