Make Huli Huli marinade:

• In a large bowl, combine the ketchup with the brown sugar, soy sauce, apple cider vinegar, minced garlic, grated ginger, and sriracha. Mix until the sugar dissolves. Reserve ¼ of the marinade for basting.
  
• Place the chicken thighs in the bowl with the marinade, turn until all are well coated, cover with plastic wrap, and refrigerate for 30 minutes or overnight.
  
• Heat the grill or grill pan. Remove any excess marinade and discard it. Cook the thighs for 6 minutes on each side or until fully cooked, basting them once on each side with the reserved marinade. Serve with grilled pineapple on the side and sliced green onions on top.