Heat a nonstick skillet coated with cooking spray over medium-high heat.
Add pork and cook until golden brown, about 8 to 10 minutes; remove from skillet and set aside. Drain any remaining fat from skillet.
Drain pineapple chunks, reserving juice; set aside.
Combine water, vinegar, sugar, cornstarch, salt, soy sauce and reserved pineapple juice in a small bowl; add to skillet and cook until sauce is slightly thickened, about 2 minutes. Add pork; cook covered over low heat until meat is tender, stirring occasionally, about 30 minutes.
Add peppers, onion and pineapple chunks; cook 5 minutes. Serve over rice. Yields about 1 cup of pork and 1/2 cup of rice per serving.