01 - Whisk together soy sauce, pineapple juice, olive oil, garlic powder, and black pepper in a bowl. Submerge chicken breasts in the marinade and refrigerate 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 the cornstarch slurry and continue cooking for 1-2 minutes until the sauce thickens to a glossy consistency. Remove from heat and reserve.
03 - Heat grill or grill pan to medium-high temperature, approximately 375-400°F.
04 - Remove chicken from marinade and place on the hot 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 charred and caramelized.
05 - Lightly butter burger buns if desired and place cut-side down on the grill for 30-60 seconds until golden brown and lightly crisped.
06 - Spread mayonnaise on the bottom bun. Layer with lettuce leaf, grilled chicken breast, and drizzle generously with teriyaki sauce. Add grilled pineapple ring, tomato slice, and red onion. Cap with the top bun and press gently.
07 - Serve immediately while chicken is hot and pineapple retains its grill marks. Pair with sweet potato fries or tropical slaw if desired.