Step 1: In a large bowl or a sturdy resealable bag, combine the pineapple juice, low-sodium soy sauce, brown sugar, minced fresh ginger, minced garlic, rice vinegar, and sesame oil. Whisk or shake well until the brown sugar is fully dissolved.
Step 2: Add the chicken thighs to the marinade, ensuring each piece is thoroughly coated. Cover the bowl or seal the bag and refrigerate for at least 30 minutes, or ideally for 2-4 hours. You can marinate overnight for maximum flavor.
Step 3: Preheat your grill to medium-high heat. If using an oven, preheat to 400°F (200°C) and line a baking sheet with parchment paper or foil. If pan-frying, heat a large skillet over medium-high heat with a tablespoon of oil.
Step 4: Remove the chicken from the marinade, allowing any excess to drip off (discard the used marinade). Grill the chicken for 5-7 minutes per side, or until an internal temperature reaches 165°F (74°C) and the chicken is nicely charred. If baking, place chicken on the prepared baking sheet and bake for 20-25 minutes, flipping halfway, until cooked through and lightly caramelized. For pan-frying, cook for 6-8 minutes per side.
Step 5: (Optional Glaze) While the chicken cooks, you can create a simple glaze by simmering a separate half batch of the marinade ingredients in a small saucepan over medium heat for 5-7 minutes, until slightly thickened. Brush this glaze over the chicken during the last few minutes of cooking.
Step 6: Once cooked, let the chicken rest for 5 minutes before slicing or serving. Garnish with fresh pineapple chunks, chopped green onions, and a sprinkle of toasted sesame seeds.