Dehydrated chicken breast, liver, lung, etc. are all great treats. Alternatively, if you want to go with a small baked piece, I like to use soft types like Zuke's or Merricks, Orijen, or My Mighty Wolf for example. If one of the first two ingredients isn't an actual protein, then I don't use it. Not that they're all "perfect", but I'd rather my first ingredient be a quality controlled meat protein that isn't followed by a whole bunch of crap. Here's some examples:
Milk Bone Original Biscuits:
Wheat Flour, Wheat Bran, Meat and Bone Meal, Milk, Wheat Germ, Beef Fat (Preserved with BHA), Salt, Natural Flavor, Dicalcium Phosphate, Calcium Carbonate, Brewers Dried Yeast, Malted Barley Flour, Sodium Metabisulfite (Used as a Preservative), Choline Chloride, Minerals (Ferrous Sulfate, Zinc Oxide, Manganous Oxide, Copper Sulfate, Calcium Iodate, Sodium Selenite), Vitamins (Vitamin E Supplement, Vitamin A Supplement, Niacin Supplement, d-Calcium Pantothenate, Riboflavin Supplement, Pyridoxine Hydrochloride, Vitamin D3 Supplement, Folic Acid, Biotin, Vitamin B12 Supplement), BHA (used as a preservative).
My Mighty Wolf Dog Treat - Natural, Grain Free, Pork Sausage
Fresh Ground Pork Liver, Pork Gelatin, Sweet Potato, Pork Fat, Molasses, Vegetable Glycerine, Pumpkin, Sea Salt, Bisulphate Of Soda (A Natural Acidifier), Calcium Ascorbate (A Natural Source of Vitamin C), Mixed Tocopherols (A Natural Preservative), Sorbic Acid (A Natural Preservative)
Dried sweet potato chews: rinse the sweet potato. Slice it making slices a little less than 1/4 inch thick. Bake in a preheated oven at 200F for about 2-3 hrs flip them over at the half mark of the time you intend to bake them. (time depends on how soft or how dried you want them). When cooled refrigerate. They are good for humans also.
Meatballs: make the meatballs about the size of thumbnail. Take about 1/4 pound of 80% or 85% lean Hamburg. Add some garlic powder, parsley, and some good Romano or Parmesan cheese. Mix all together. Take 1 egg and scramble it in a separate bowl, then add a little of the scrambled egg in the Hamburg mixture to moisten the mixture but don't make it soggy. Probably about 1/8 to one 1/4 of the scrambled egg. Make the meatballs then boil them for 2 minutes. Then rinse them in hot water (this will clean off any grease). Dry them and let them cool and refridgerate or freeze for later use.
I don't have exact measurements for the ingredients because I learned from my mom who never measured, just knew by eyeballing the amount and the texture and smell how much of what was needed. I changed the recipe a little to make them for my boy and I found that boiling them rather than frying them cuts down the cooking time, eliminates the grease and the meatballs don't harden and are more soft and rubbery in texture plus they don't fall apart as easily. You can make the balls bigger (boil them a little longer) and then just cut them in 1/2 or 1/4 After boiling.
If using treats for training, you want to use soft treats that the pup can swallow easily without much or any chew time. This keeps his focus on you. That's been my experience with my boy.
If you scroll through the health and nutrition section there are other threads with more ideas/suggestions.
I get Red Barn meat rolls. Easy to make any size I want and convenient. Not as healthy as home made meatballs but one of the few treats with very little sweetener. It does have sucrose but because it is so very sweet they don't have to add much. I find that most treats have some sort of sweetener in them and I try to avoid it as much as I can.
Other times I'll use a bit of chicken or pork. Sometimes bits of beef. Sometimes liverwurst but I usually keep that in reserve for covering pills for the few times I had to give them.