In a bowl combine brown sugar, corn starch and ginger. Add enough water to reserved pineapple juiice to measure 1/2 cup, stir into corn starch mixture until smooth, add vinegar and soy sauce. Set aside.
In a large skillet coated with nonstick spray, stir fry onion (cut in wedges), peppers (cut into 1 inch pieces) til crisp tender. To prevent burning, you may need to spray several times. Add garlic powder and stir fry a minute or so longer.
Add the tomato, kidney beans and reserved pineapple, cook and stir for 2 to 3 minutes or until heated through.
Stir soy sauce mixture into mixture, cook until thickened.