In a large bowl, whisk together the barbecue sauce, pineapple juice, brown sugar, soy sauce, garlic powder, onion powder, black pepper, and red pepper flakes.
Place the frozen meatballs in the slow cooker.
Pour the sauce mixture over the meatballs, ensuring they are well coated.
Add the drained pineapple chunks to the slow cooker, mixing gently to combine.
Cover and cook on low for 4-5 hours or on high for 2-3 hours, until the meatballs are heated through and the sauce is thickened.
Stir the meatballs occasionally to ensure they are evenly coated with the sauce.
Garnish with fresh parsley before serving, if desired. Serve warm.