Coat grill rack with cooking spray before starting the grill. Drain pineapple, reserving 1/4 cup juice (discard remaining juice or save for another use); set pineapple aside. In a bowl, combine the bread crumbs, onions, red pepper, soy sauce, salt and reserved pineapple juice. Crumble turkey over mixture and mix well. Shape into four patties.
Grill, covered, over medium heat for 3 minutes on each side. Brush with teriyaki sauce. Grill 4-6 minutes longer on each side or until meat is no longer pink and a meat thermometer reads 165°. Grill pineapple slices for 2 minutes on each side, basting occasionally with teriyaki sauce. Warm buns on grill; top each with a burger and pineapple slice.