Cut steak into 3 cm cubes and dredge with flour. Brown meat cubes on all sides in hot fat. Add water and salt. Simmer gently until meat is tender. Clean green peppers and cut into 3 cm squares. Boil 10 minutes and drain. Add pepper squares and pneapple chunks to browned meat. SAUCE: Combine cornstarch, pineapple juice, vinegar, sugar and soy sauce and cook until sauce is clear and thick. Pour sauce over meat mixture and simmer 5 minutes. Serve over Chinese noodles or cooked rice.