In a large bowl, combine the first six ingredients. Add ground beef over mixture and mix well. Shape into eight 3/4-in.-thick patties.⠀⠀⠀⠀⠀⠀⠀⠀⠀
Grill, uncovered, over medium-hot heat for 3 minutes on each side. Brush with soy sauce. Continue grilling for 4-6 minutes or until juices run clear, basting and turning several times.⠀⠀⠀⠀⠀⠀⠀⠀⠀
During the last 4 minutes, grill the pineapple slices until browned, turning once. Serve burgers and pineapple on buns with lettuce.