01 - Whisk together soy sauce, pineapple juice, olive oil, garlic powder, and black pepper in a shallow dish. Add chicken breasts, turning to coat evenly. Marinate for at least 15 minutes, or refrigerate 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, then stir in cornstarch slurry. Cook for 1-2 minutes, stirring constantly until sauce thickens to a glossy consistency. Remove from heat and set aside.
03 - Heat grill or grill pan to medium-high temperature (approximately 375°F to 400°F). Ensure grates are clean and lightly oiled to prevent sticking.
04 - Remove chicken from marinade and discard excess liquid. Grill chicken for 5-6 minutes per side until internal temperature reaches 165°F and juices run clear. During the final 2 minutes of cooking, place pineapple rings on the grill until marked and lightly caramelized.
05 - Place burger buns cut-side down on the grill for 30-60 seconds until golden brown and lightly crisped.
06 - Spread mayonnaise on toasted bottom buns. Layer with lettuce leaves, grilled chicken breasts, and drizzle generously with teriyaki sauce. Add grilled pineapple rings, tomato slices, and red onion. Cap with top buns and press gently.
07 - Transfer assembled burgers to plates or serving platter. Serve while chicken is hot and pineapple retains its grill marks.