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 fully 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 remaining marinade over the chicken, ensuring all pieces are coated. Cover and refrigerate for at least 2 hours, up to overnight for maximum flavor.
04 - Heat grill to medium-high, approximately 400°F. Lightly oil the grates to prevent sticking.
05 - Remove chicken from marinade and discard the used liquid. Pat the pieces dry with paper towels.
06 - Place chicken skin side down on the grill. Cook for 6-8 minutes, then flip and grill another 6-8 minutes on the second side.
07 - Brush chicken with the reserved marinade. Continue grilling, turning and basting every 2-3 minutes until the chicken reaches an internal temperature of 165°F and develops a caramelized exterior, approximately 20-25 minutes total cooking time.
08 - Transfer chicken to a platter and let rest for 5 minutes. Garnish with scallions, sesame seeds, and diced pineapple if desired. Serve hot.