Preheat oven to 350 degrees F.
In deep non-greased baking pan, add the thawed meatballs. Top the meatballs with the pineapple chunks. In a medium bowl add the mustard, red and green onion, and garlic. Mix well. Top the meatballs and pineapple with the mustard sauce. Add the Sweet and Sour Sauce and season with black pepper.
Bake for 30 minutes. Remove from the oven; add the remaining pineapple juice, stir to combine, and place back in the oven for the remaining 30 minutes. Serve while hot.
In a saucepot, mix all ingredients together. Cook on high heat. Keep your eye on it. Do not walk away. Cook for 2 minutes and stir. After 3 to 4 minutes, take it off the heat and mix for 2 minutes. Use it same day or keep in the refrigerator for about 2 to 3 weeks at the maximum.