Non-food rewards.
How about some alternatives to food as a treat?
Treats for kitties don't always have to be food. I think the civies want the treat too, but most of all, they wonder what is going on and want some special attention too.
A treat can be a hug or a little bit of brushing or petting them or picking them up or a two handed massage or talking to them and telling them what good kitties they are or ear scritchies or play time.
My civie Monet loves some extra special attention, being picked up and slung over my shoulder and a close up snuggle. He is my lap kitty and the only one that will crawl up on top of me in the evenings when I am laying on the couch reading a book.
My civie Delta hates being picked up but she loves a little two handed massage, running my fingers through her fur, one hand on each side and getting down into the skin a bit and massaging from shoulders to butt. After a year and a half, I'm just starting to get this skittish semi-feral kitty used to me picking her up and putting her in my lap. But she'll only stay there if she is getting the full body massage.
My sugarhunk Wink loves head and ear scritchies and will purr up a little storm. No picking up please, and no petting unless he is in the mood. When he is not, he dives away from my hand. ohmygod_smile
Find something special to do for each of your kitties. Even if it's for just a couple of minutes.