In a medium bowl, whisk together pineapple juice, soy sauce, brown sugar, honey, rice vinegar, sesame oil, minced garlic, and grated fresh ginger until the sugar dissolves completely.

Place the chicken thighs into a resealable bag or shallow dish. Pour half of the marinade over the chicken and reserve the other half. Seal the bag or cover the dish and refrigerate for at least 1 hour, preferably overnight.

Preheat your grill to medium-high heat, around 400°F (200°C), or heat a non-stick skillet over medium heat with a drizzle of oil.

Grill the marinated chicken thighs for 5–7 minutes on each side, until cooked to an internal temperature of 165°F (74°C). For skillet cooking, cook for 6–8 minutes per side, turning only once.

In a small saucepan, bring the reserved marinade to a boil over medium-high heat. Reduce heat and simmer for about 5 minutes. If a thicker sauce is desired, mix cornstarch with water and stir into the sauce, cooking for an additional 1-2 minutes until thickened.

Brush thickened sauce over the cooked chicken during the last minute of grilling. Drizzle any remaining sauce on top when serving. Garnish with sliced green onions and sesame seeds.