LOL In a year I think the chins here are lucky to get treats maybe a half dozen times. Most of the chins are in the rooms that I don't keep any treats in so they don't get much of anything.
However, if I do give treats, plain shredded wheat is probably the favorite. Followed by apple treats, rosehips, dried papaya, dried apple and very, very occasionally other things. I like to recommend rosehips for pets because of the vitamin C and the fact that they aren't going to really be able to overfeed them as much as other treats.
One treat a day is plenty if treats are given at all. You want the chins to fill up their little bellies with their pellets and hay! Overtreating can lead to picky chins and chins that do not get proper nutrition.
(Like everyone else said....)