Add Pork (750 gram), Onion (1), Breadcrumbs (1 cup), and Egg (1) into a mixing bowl and mix it together. Take a teaspoonful of mixture and roll a ball by hands. Continue with the rest.
Put oil into a fry pan and cook the meatballs in batches to brown the outside for about 4 to 5 minutes. Transfer them to a large casserole dish.
Drain the juice of Canned Diced Pineapple (400 gram) into a cup. Add Corn Flour (2 tablespoon), and stir it using a spoon. Then add Distilled White Vinegar (2 tablespoon), Brown Sugar (1 tablespoon), Soy Sauce (1 tablespoon), Ketchup (1 tablespoon), Garlic (1 teaspoon), the pineapple pieces, Bell Pepper (1), Water (1 cup). Mix everything together.
Pour the sauce into the casserole. Preheat the oven to 200 degrees C (400 degrees F). Cook for about 30 minutes or until the meatballs are fully cooked through.