I use lots of variety in my treats, to keep them guessing. And my dogs really like grain-free kibble as treats. Especially if it's in the same bag as really gross squishy yummy stuff. My dogs love chicken organs (hearts, gizzards and lungs only because I don't like liver) sprinkled in garlic powder and baked until they're a bit dehydrated. They also love a hot dog (or a turkey/chicken/soydog) microwaved for 1+ minute so it's really tough. Ground beef with some garlic powder is also a favorite. Fishy treats that make me gag are super popular with them, like Yummy Chummies. You can mix in some kibble (preferably grain-free) with high value treats, leave them in the fridge together overnight, and the kibble will be much more exciting. You can also give your dog a spoonful or two of plain canned pumpkin after a training sessions to keep the poops firm, and some yogurt or digestive enzymes to help build good flora.