Preheat the oven to 400 degrees. Coat a baking sheet with cooking spray.
Cut the sweet potatoes in half lengthwise and place them cut side down on the prepared baking sheet.
Place into the oven and roast for 30-40 minutes, or until very tender. Remove from the oven and allow to cool.
Reduce the oven to 375 degrees. Line a baking sheet with parchment paper.
Scoop out the cooled insides of the sweet potatoes into a large mixing bowl; discard the skins. Add the grated apple and eggs to the bowl. Slowly add the flour, one cup at a time, mixing well between each addition.
Working on a lightly floured surface, knead the dough 3-4 times until it comes together. Using a rolling pin, roll the dough to 1/4-inch thickness. Use more flour as needed.
Use a cookie cutter to cut out the desired shape and place it onto the prepared baking sheet.
Place into oven and bake until the edges are golden brown, about 20-25 minutes. Remove from the oven and allow to cool completely on a wire rack.
Store in a sealed container in the refrigerator or freezer. My dog loves them right out of the freezer. Enjoy.