
Make the marinade by whisking together the pineapple juice, ketchup, soy sauce, cooking wine, brown sugar, sriracha, rice vinegar, sesame oil, ginger, and garlic until the sugar dissolves.
Reserve 3/4 cup of the marinade in a separate bowl for basting during cooking.
Place the chicken thighs in a glass or ceramic dish and pour the remaining marinade over the top. Turn to coat well, cover, and refrigerate for 24 to 48 hours.
When ready to cook, lightly oil the grill grates and preheat the grill to medium-high heat. If using a skillet, heat the vegetable oil in a large skillet over medium-high heat.
Remove the chicken from the marinade and let the excess drip off. Discard the used marinade, then place the chicken on the grill or in the skillet.
Cook the first side for 2 to 3 minutes, until lightly charred and golden. Flip and cook the second side for 2 minutes.
Brush the chicken generously with the reserved marinade, then flip and cook for 1 minute. Continue flipping and basting every minute until the chicken is glossy, caramelized, and cooked through, about 10 to 12 minutes total.
Check for doneness with an instant-read thermometer. Chicken thighs should reach 75 C / 167 F in the thickest part.
Transfer the chicken to a plate, loosely tent with foil, and let it rest for 3 minutes before serving.
Garnish with sliced green onion and serve with pineapple slices, if desired.