Preheat oven to 375°F (190°C).
In a mixing bowl, combine ground beef, breadcrumbs, egg, milk, salt, black pepper, and garlic powder. Mix well.
Form the mixture into small meatballs and place them on a baking sheet.
Bake in the preheated oven for 20 minutes, or until browned and cooked through.
In a saucepan, combine ketchup, brown sugar, vinegar, and Worcestershire sauce. Cook over medium heat until the sugar is dissolved and the sauce is heated through.
Add the baked meatballs to the saucepan and stir to coat them in the sauce.
Simmer for 10 minutes, stirring occasionally.
Serve hot.