01 - Whisk together soy sauce, pineapple juice, olive oil, garlic powder, and black pepper in a bowl. Submerge chicken breasts in the mixture and let 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. Bring to a gentle simmer over medium heat. Stir in the cornstarch slurry and continue cooking for 1-2 minutes until sauce achieves desired consistency. Remove from heat and set aside.
03 - Heat grill or grill pan to medium-high temperature, approximately 375-400°F.
04 - Place marinated chicken on the preheated grill. 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 visible grill marks.
05 - Place cut sides of burger buns on the grill for 30-60 seconds until lightly golden and crisp.
06 - Spread mayonnaise on bottom bun if desired. Layer lettuce leaf, grilled chicken breast, and drizzle generously with teriyaki sauce. Add grilled pineapple ring, tomato slice, and red onion. Complete with top bun and serve immediately.