01 - In a medium bowl, whisk together the soy sauce, pineapple juice, brown sugar, olive oil, garlic, ginger, and black pepper until the sugar dissolves and the mixture is well combined.
02 - Place the chicken breasts in a large resealable plastic bag or shallow dish. Pour the marinade over the chicken, turning each piece to coat evenly. Seal and refrigerate for at least 30 minutes, or up to 4 hours for deeper flavor penetration.
03 - Preheat your grill to medium-high heat (approximately 375°F to 400°F). Lightly oil the grates to prevent sticking.
04 - Remove the chicken from the marinade, allowing excess 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.
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 plates and top each portion with grilled pineapple rings. Sprinkle with sliced green onions and sesame seeds if desired. Serve immediately.