In a medium bowl, whisk together all the Huli Huli Sauce ingredients: pineapple juice, soy sauce, brown sugar, ketchup, rice vinegar, minced garlic, and grated ginger. Whisk until the brown sugar is completely dissolved.

Set aside 1/2 cup of the marinade to use for basting later. Place the chicken thighs in a large resealable plastic bag or a shallow dish. Pour the rest of the marinade over the chicken, making sure it's fully coated. Seal the bag or cover the dish and refrigerate for at least 4 hours, or preferably overnight.

Preheat your grill to medium heat (about 375-450°F). Make sure the grates are clean and lightly oiled to prevent the chicken from sticking.

Remove the chicken from the marinade, allowing any excess to drip off. Discard the used marinade. Place the chicken on the preheated grill and cook for about 6-8 minutes per side, or until cooked through.

While the chicken is grilling, pour the reserved 1/2 cup of marinade into a small saucepan. Bring to a boil and let it simmer for 2-3 minutes to thicken slightly. This will be your glaze.

During the last few minutes of cooking, brush the thickened glaze over both sides of the chicken. This will create a beautiful, caramelized crust. Cook until the internal temperature of the chicken reaches 165°F (74°C).

Remove the chicken from the grill and let it rest for 5 minutes before slicing or serving. This helps keep it juicy. Serve warm and enjoy!