In a mixing bowl, whisk together ½ cup of soy sauce, ¼ cup of brown sugar, ½ cup of pineapple juice, ¼ cup of ketchup, 2 tablespoons of vegetable oil, 2 teaspoons of minced ginger, and 2 cloves of minced garlic. Add 2 tablespoons of rice vinegar and a pinch of black pepper.

Place your boneless, skinless chicken thighs into a resealable plastic bag. Pour the prepared marinade over the chicken, seal the bag tightly, and refrigerate for at least 1 hour.

Preheat your grill to medium-high heat for about 15 minutes, aiming for a temperature of around 400°F (204°C).

Remove the marinated chicken thighs from the refrigerator and let them sit for a few minutes at room temperature. Place the chicken directly onto the preheated grill grate.

Cook for approximately 6-8 minutes per side, flipping once, until the internal temperature reaches 165°F (75°C).

Optionally, use a basting brush to apply some of the leftover marinade to the chicken during the last few minutes of grilling.

Remove the chicken from the grill and let it rest on a cutting board for about 5 minutes before slicing.

Before serving, slice the rested chicken into pieces and garnish with chopped green onions and sesame seeds if desired.