Preheat oven to 350 degrees F. Grease the baking sheet or parchment-lined baking sheet and set aside. Make breadcrumbs by blending 1-inch pieces of bread in a blender or food processor and scooping breadcrumbs into a large mixing bowl. Stir in walnut, sage, oregano, and basil.
In a food processor or blender, combine the tofu, liquid aminos, nutritional yeast flakes, tapioca starch, onion powder, garlic, and sea salt. Process.
Pour the blended mixture into the bowl with seasoned breadcrumbs and mix well. Form into balls and bake for 30 minutes, turning meatballs after 15 minutes. Transfer tofu meatballs to a serving dish, spoon sweet and sour sauce over the tofu meatballs, and serve.