In a small bowl or measuring cup whisk together 1/2 cup of the pineapple juice and cornstarch until dissolved to make a slurry. Set aside.
In a large skillet stir together the brown sugar, vinegar, ketchup, soy sauce, and 2 cups of the pineapple juice. Bring to a boil over med-high heat.
Whisk the slurry into the sauce and bring to a boil. Add in meatballs and sriracha and simmer until the sauce is thickened and meatballs are heated, about 8-10 minutes. Add pineapple chunks.
Serve over cooked rice and top with scallions.
Just as delicious for leftovers!