01 - In a medium bowl, whisk together the soy sauce, pineapple juice, brown sugar, olive oil, minced garlic, grated ginger, and black pepper until the sugar dissolves and the mixture is well blended.
02 - Place the chicken breasts in a large resealable plastic bag or shallow dish. Pour the marinade over the chicken, seal, and turn to coat each piece evenly. Refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor penetration.
03 - Preheat an outdoor grill or grill pan to medium-high heat (approximately 400°F). Lightly oil the grates using a paper towel dipped in vegetable oil to prevent sticking.
04 - Remove the chicken from the marinade, allowing excess liquid to drip off. Discard the remaining marinade. Grill the chicken for 5 to 7 minutes per side, or until the internal temperature reaches 165°F when measured with a meat thermometer at the thickest part.
05 - While the chicken cooks, place the pineapple rings on the grill. Cook for 2 to 3 minutes per side until grill marks appear and the fruit is lightly caramelized.
06 - Transfer the grilled chicken to serving plates and top each breast with a grilled pineapple ring. Garnish with sliced green onions and sesame seeds if desired. Serve immediately.