Step 1: In a large bowl, whisk together pineapple juice, soy sauce, ketchup, brown sugar, rice vinegar, ginger, and garlic to make the marinade.

Step 2: Place the chicken breasts in a resealable bag or shallow dish and pour the marinade over them. Seal or cover and refrigerate for at least 2 hours.

Step 3: Preheat your grill to medium-high heat. Brush the grill grates with vegetable oil to prevent sticking.

Step 4: Remove the chicken from the marinade, letting excess drip off. Grill the chicken for about 6-7 minutes per side, or until fully cooked.

Step 5: While grilling, occasionally baste the chicken with the reserved marinade, but stop basting during the last few minutes of cooking to avoid cross-contamination.

Step 6: Grill the pineapple rings for about 2 minutes per side until they are caramelized and have grill marks.

Step 7: Remove the chicken and pineapple from the grill and let the chicken rest for a few minutes before slicing.

Step 8: Serve the grilled chicken over a bed of white rice, topped with grilled pineapple rings and garnished with chopped green onions.