01 - In a large bowl, whisk together soy sauce, pineapple juice, brown sugar, ketchup, rice vinegar, ginger, garlic, sesame oil, honey, smoked paprika, and pepper until well combined.
02 - Reserve 1/2 cup of the marinade for basting; set aside.
03 - Place chicken pieces in a large resealable bag or shallow dish. Pour remaining marinade over the chicken, ensuring all pieces are well coated. Cover and refrigerate for at least 2 hours (up to overnight).
04 - Preheat grill to medium-high heat (about 400°F). Oil the grates to prevent sticking.
05 - Remove chicken from marinade; discard used marinade. Pat chicken dry lightly with paper towels.
06 - Grill chicken, skin side down, for 6-8 minutes. Flip and grill for another 6-8 minutes.
07 - Brush chicken with reserved marinade and continue grilling, turning and basting every 2-3 minutes, until cooked through and nicely caramelized (internal temperature should reach 165°F), about 20-25 minutes total.
08 - Remove from grill and let rest for 5 minutes. Garnish with scallions, sesame seeds, and pineapple if desired. Serve hot.