01 - Whisk together soy sauce, pineapple juice, olive oil, garlic powder, and black pepper in a bowl. Add chicken breasts, ensuring even coating. 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 gentle simmer. Whisk in cornstarch slurry and cook for 1-2 minutes until sauce thickens noticeably. 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 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 grill marks.
05 - Place burger buns cut-side down on the grill for 30-60 seconds until lightly golden and crispy.
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. Cap with top bun and press gently.
07 - Transfer assembled burgers to plates and serve immediately while chicken is hot and pineapple is warm.