Drain pineapple, reserving 1/4 cup juice; set juice aside. Alternate pineapple chunks, fish, and green pepper on 6 wooden skewers. Place kabobs in a large shallow dish; set aside.
Combine reserved pineapple juice, soy sauce, sherry, brown sugar, ginger, mustard, and garlic, stirring well. Pour marinade over kabobs; cover and marinate at least 1 hour in refrigerator.
Remove kabobs from marinade, reserving marinade. Grill kabobs over medium-hot coals 15 minutes or until fish flakes easily when tested with a fork. Baste kabobs frequently with marinade. Serve with hot cooked rice.