Preheat your oven to 375°F (190°C).
In a large bowl, combine ground beef, breadcrumbs, chopped onion, egg, garlic powder, salt, and pepper.
Mix until well combined, then form the mixture into meatballs, about 1 inch in diameter.
Place the meatballs on a baking sheet lined with parchment paper.
Bake for 20 minutes or until browned and cooked through.
While the meatballs are baking, prepare the sauce by combining ketchup, vinegar, brown sugar, and soy sauce in a saucepan.
Heat the sauce over medium heat, stirring until the sugar dissolves.
Add the pineapple chunks to the sauce and bring it to a simmer.
Once the meatballs are cooked, add them to the sauce and gently stir to coat.
Simmer for an additional 5 minutes to let the flavors meld together.