Place chicken wings in a large zipper-lock freezer bag. Set aside.
In a medium bowl, whisk together pineapple juice, soy sauce, light brown sugar, chicken stock, ginger, garlic, and sriracha. Pour half of sauce into bag of chicken, seal bag, and toss to coat. Cover remaining sauce in bowl with plastic wrap and refrigerate. Place bag of chicken in refrigerator and let marinate for at least 1 hour and up to 8 hours.
Light 1 chimney full of charcoal. When all charcoal is lit and covered with gray ash, pour out and spread coals evenly over half of coal grate. Alternatively, set half the burners of a gas grill to high heat. Set cooking grate in place, cover grill, and allow to preheat for 5 minutes. Clean and oil grilling grate.
Remove wings from marinade, allowing excess to drip off; discard marinade. Place wings on cooler side of grill, cover with vents partially open, and cook, occasionally brushing with reserved often with sauce to build up a nice glaze.sauce and turning wings, until wings are well browned and cooked through, about 30 minutes. Move wings to hot side of grill and cook until browned all over, about 3 minutes per side, brushing.
Serve chicken wings with thinly sliced scallions and grilled pineapple, if desired.