In a small bowl, combine the brown sugar, vinegar, ketchup, and soy sauce. Pour half into a large resealable plastic bag; add pork. Seal bag and turn to coat; refrigerate for 30 minutes. Set remaining marinade aside.
Drain and discard marinade from pork. In a large skillet, cook pork in oil for 3 minutes. Add the onion, carrots, green pepper, garlic and ginger; saute until pork is no longer pink. Add reserved marinade.
Bring to a boil; cook for 1 minute. Stir in the pineapple. Serve with rice if desired.