Hmm, my cats love the Bil - Jac treats, which for your tyically store bought treat, has a good amount of animal products in it, instead of things just like wheat flour lol.
I also give them left overs of my meals, things like cut up chicken, rice, hamberger, any left over steak, raw & cooked egg.
There's lots of thigns I feed for a treat, or part of their meals.