01 - Whisk together soy sauce, pineapple juice, brown sugar, ketchup, rice vinegar, ginger, garlic, sesame oil, honey, smoked paprika, and pepper in a large bowl until thoroughly combined.
02 - Measure out 1/2 cup of the marinade and set aside separately for basting during grilling.
03 - Place chicken pieces in a large resealable bag or shallow dish. Pour the remaining marinade over the chicken, ensuring all pieces are evenly coated. Cover and refrigerate for at least 2 hours, preferably overnight for maximum flavor.
04 - Heat grill to medium-high temperature (approximately 400°F). Lightly oil the grates to prevent sticking.
05 - Remove chicken from the marinade and discard the used liquid. Pat the chicken pieces dry with paper towels for better searing.
06 - Place chicken on the grill skin side down. Cook for 6-8 minutes, then flip and cook for an additional 6-8 minutes.
07 - Brush chicken with the reserved marinade. Continue grilling while turning and basting every 2-3 minutes until the internal temperature reaches 165°F and the exterior is caramelized, approximately 20-25 minutes total cooking time.
08 - Transfer chicken from grill and let rest for 5 minutes to allow juices to redistribute. Garnish with sliced scallions, toasted sesame seeds, and diced pineapple if desired. Serve immediately.