Combine ground beef, breadcrumbs, egg, minced garlic, salt, and pepper in a bowl.
Shape the mixture into small, evenly sized meatballs.
Heat oil in a skillet and cook the meatballs until browned and fully cooked.
In a separate pan, combine ketchup, vinegar, brown sugar, and a little soy sauce to prepare the sweet and sour sauce.
Add the cooked meatballs to the sauce and simmer for 5–10 minutes until they are well coated and the sauce thickens.
Garnish with sesame seeds or chopped green onions and serve hot with rice or noodles.