Jackson is really picky with his treats. I usually give him a biscuit-type treat at bedtime which he happily accepts but as for a 'reward' (trick training etc) he usually won't work terribly hard for a hard biscuit type treat. Just not yummy enough I guess.
Zuke's have little tiny training treats that are great and low calorie. Also he likes these:
https://www.chewy.com/pet-botanics-t...acon/dp/102764 -- they are both tiny, chewy little treats.
He actually really likes these biscuits.
https://www.chewy.com/purina-beyond-...cken/dp/126550
Sometimes I give him one as a bed time snack. But they can be broken up into smaller pieces.
These are little and easy to break too but they're biscuit-style and Jackson actually will do training for these surprisingly.
https://www.chewy.com/natural-balanc...mited/dp/33275
Anything freeze dried he loves of course.