In a large mixing bowl, combine the ground chicken, breadcrumbs, green onions, teriyaki sauce, crushed pineapple, garlic powder, salt, and black pepper. Mix until well combined, but do not overmix.
Divide the mixture into four equal portions and shape each portion into a patty.
Preheat a grill or skillet over medium heat. Lightly grease with cooking spray or a little oil.
Cook the patties for about 5-6 minutes on each side, or until they reach an internal temperature of 165°F.
Toast the hamburger buns on the grill or in a toaster until golden brown.
Assemble the burgers by placing a chicken patty on each bun, then top with lettuce, tomato, and red onion. Serve immediately.