Are these little reward treats just for going in or treats when they go in and get left for a while? If I'm leaving her in her crate for a while, I give her some type of yummy chew rather than a treat: a bully stick, cow ear, stuffed cow hoof . . . it lasts a lot longer
If I'm just reinforcing crate behavior, I used all sorts of things . . . but I think the Charlie Bears are a good pick.