My late pup Guapo used to love these things called Greenies. It would take him a few minutes to chew them. Plus, they're good for a dog's teeth. Guapo lived to be 15. One thing he never had was dental issues. His teeth were always clean. His brother from the same litter on the other hand, never like hard or crunch treats. He ended up having 80 percent of his teeth pulled and now is on canned food the rest of his life.
Greenies were loved by all of my dogs through the years. A little pricey, but great for the teeth.
We feed our mini aussies green beans quite often. They eat all kinds of vegetables; Romaine lettuce, carrots, broccoli, Brussels sprouts, cucumber, tomato, potatoes and fruit also. They love apples, water melon, canteloupe, blueberries. They really like them. You can blend the fruits together and freeze them too. They are great for hot days. Grapes and raisins are toxic though. Read up on what they cannot have.
Chicken gizzards and livers are great too. I cook them and refrigerate in a Tupperware dish. For some reason they will not eat them raw. The livers are a great pill delivery system too. They are soft and you can push a pill right into them easily. Very inexpensive.
One thing that you can try that is very healthy is chicken or turkey feet raw. Mine won't eat them but some dogs love them. They are great for their joints.
Raw eggs, especially if they eat the shells. The shell membrane is very nutritious. The Shell has calcium. The egg is a complete meal. Diesel and Daisy won't eat the shell even if I crush it. You can cook them too but they are not quite as healthy that way. When I make hard boiled eggs they get all of the eggs that break open and become misshapen.
We buy free range eggs from a person that has chickens. The yolks are more orange and she doesn't add anything to the feed. Plus she lets them roam for insects. The rest I get at the grocery store or butcher and are inexpensive.
My daughter makes them treats using pumpkin, oatmeal and peanut butter. She even has a mold that looks like dog biscuits.