01 - Combine soy sauce, pineapple juice, olive oil, garlic powder, and black pepper in a bowl. Add chicken breasts and marinate for at least 15 minutes, up to 2 hours for deeper flavor penetration.
02 - In a small saucepan, mix soy sauce, pineapple juice, brown sugar, and rice vinegar. Bring to a simmer over medium heat. Stir in the cornstarch slurry and cook for 1-2 minutes until thickened. Remove from heat and set aside.
03 - Preheat grill or grill pan to medium-high heat, approximately 375-400°F.
04 - Grill marinated chicken breasts for 5-6 minutes per side until fully cooked, reaching an internal temperature of 165°F. During the final 2 minutes of cooking, place pineapple rings on the grill and cook until lightly caramelized with grill marks.
05 - Lightly toast burger buns on the grill cut-side down for 30-60 seconds until golden brown.
06 - Spread mayonnaise on the bottom bun if desired. Layer lettuce leaf, grilled chicken breast, drizzle with teriyaki sauce, add grilled pineapple ring, tomato slice, red onion slice, and crown with the top bun.
07 - Serve immediately while chicken is hot and pineapple retains its sweetness.