01 - Whisk together soy sauce, pineapple juice, olive oil, garlic powder, and black pepper in a bowl. Add chicken breasts and coat thoroughly. Marinate for at least 15 minutes, or up to 2 hours for deeper flavor penetration.
02 - Combine soy sauce, pineapple juice, brown sugar, and rice vinegar in a small saucepan over medium heat. Bring to a simmer, then stir in the cornstarch slurry. Cook for 1-2 minutes until sauce thickens to a glossy consistency. Remove from heat and set aside.
03 - Preheat grill or grill pan to medium-high heat, approximately 375-400°F. Ensure grates are clean and lightly oiled to prevent sticking.
04 - Place marinated chicken on the grill and cook for 5-6 minutes per side until internal temperature reaches 165°F. During the final 2 minutes of cooking, add pineapple rings to the grill and cook until lightly caramelized with distinct grill marks.
05 - Lightly toast burger buns on the grill cut-side down for 30-60 seconds until golden brown and slightly crisp.
06 - Spread mayonnaise on the bottom bun if using. Layer with lettuce leaf, grilled chicken breast, drizzle of teriyaki sauce, grilled pineapple ring, tomato slice, and red onion. Cap with the top bun and press gently.
07 - Serve burgers while chicken and pineapple are still warm. Extra teriyaki sauce can be passed separately for additional drizzling.