I used to work in a pet food store and tried a bunch of treat samples we had. They're not very good if you aren't a dog or a cat, turns out

There are posh producers who do 100% freeze dried meat pet food and treats. Even so, probably not something you want or need in your body.

I've tried both wet and dry cat food. The wet food was very bad, but still relatively edible. It was also the one I expected to be good (it was one of those really expensive and premium brands). The dry food, however, tasted exactly like fried anchovies. It wasn't bad, honestly.

Edit: I've also tried dog cookies. Most of them are bland, because their main ingredient is actually ash. I don't know how healthy that is. They're also pretty hard. However, there's a specific kind that is actually very tasty, and I liked it. It's way cheaper than actual human cookies, so I still buy them every once in a while, as a treat. I still don't know if they're super healthy to eat, but I've never felt sick after eating them.