In a saucepan, whisk together pineapple juice, cornstarch, water, soy sauce, vinegar, and sugar until thoroughly combined.
Set over high heat and bring to a boil then lower heat to a simmer and continue to cook until thickened, about 7 minutes.
Remove meatballs from broiler and transfer to the crock pot.
Pour prepared sauce over the meatballs.
Cover and cook on low for 2 ½ hours, or on high for 1 ½ hours until meatballs are cooked through.
Serve over rice or noodles and garnish with green onions and sesame seeds.
If serving as an appetizer, keep meatballs in the crock pot and set the crock pot on "WARM".