Preheat the oven to 375°F (190°C).

In a large bowl, combine the ground beef, breadcrumbs, milk, Parmesan cheese, parsley, egg, salt, and pepper. Mix until well combined.

Shape the mixture into small meatballs, about 1 inch in diameter, and place them on a baking sheet lined with parchment paper.

Bake the meatballs for 12-15 minutes, or until cooked through and browned.

While the meatballs are baking, prepare the sweet and sour dipping sauce. In a small saucepan, combine the ketchup, brown sugar, white vinegar, pineapple juice, soy sauce, water, garlic powder, onion powder, ginger powder, and red pepper flakes. Bring to a simmer over medium heat and cook for 5 minutes, stirring occasionally.

Once the meatballs are cooked, transfer them to a serving dish and pour the sweet and sour dipping sauce over them. Serve hot and enjoy!