My pup was refusing food for a while and dropped a bit of weight.
I mixed some pet mince (chicken) in with his canned and/or soaked dry and he gobbled it up.
The chicken mince I buy is just minced chicken frames and meat. I mixed it up half and half with whatever commercial food he was being given. (royal canin dry, nutro wet)
He gets bored easily so I need to change up the flavors too, another one I use is sardines, just a single sardine mashed up through his food will get him eating like a champ.