Teriyaki Sandwiches

Cut steak into thin bite-size slices. In a slow cooker, combine soy sauce, sugar, ginger and garlic. Add steak. Cover and cook on low for 7-9 hours or until meat is tender. Remove meat with a slotted spoon; set aside. Carefully pour liquid into a 2 cup measuring cup; skim fat. Add water to liquid to measure 1 1/2 cups. Pour into a large saucepan. Combine cornstarch and water until smooth; add to pan. Cook and stir until thick and bubbly, about 2 minutes. Add meat and heat through. Brush rolls with butter; broil 4-5 inches from heat for 2-3 minutes or until lightly toasted. Fill with meat, top with pineapple rings and green onions.