I give treats all the time. Not usually actual horse treats. But if she gets pushy she will not get anything. She tried to bite my hand once and jeesh I had never seen a horse fly backwards so fast before.
She gets candycanes, carrots, cookies and her all time favorite is sea salt and vinegar potato chips she goes crazy for those.
But she doesn't get treats everyday and usually her treat is getting her bucket of alfalfa pellets after a ride or something.