Make the cornstarch slurry to thicken the sweet and sour sauce. To a small bowl add in the cornstarch and 1/4 cup of the pineapple juice. Whisk well until the cornstarch is smooth.
To a large pan on the stove over medium heat add the pineapple juice, brown sugar, ketchup, soy sauce, and rice vinegar whisk well bring up to a simmer. Whisk in the cornstarch slurry. Stir the meatballs and bell peppers in. Let simmer for 10 minutes or until the sauce thickens. Serve.