Creating Polynesian Chicken is easy when you follow these steps:

1. Prepare the Marinade: In a bowl, combine pineapple juice, soy sauce, brown sugar, rice vinegar, ginger, garlic, and sesame oil. Whisk until well mixed.
2. Marinate the Chicken: Place the chicken breasts in a resealable plastic bag or a shallow dish. Pour the marinade over the chicken, ensuring it’s well coated. Seal the bag or cover the dish and refrigerate for at least 1 hour, or overnight for maximum flavor.
3. Preheat the Grill or Oven: If grilling, preheat your grill to medium-high heat. If baking, preheat your oven to 400°F (200°C).
4. Prepare the Vegetables: While the chicken is marinating, slice the bell peppers and onion. Set aside.
5. Cook the Chicken: Remove the chicken from the marinade, reserving the marinade for later. Grill the chicken for 6-7 minutes on each side or until fully cooked. If baking, place the chicken on a baking sheet and bake for 25-30 minutes.
6. Sauté the Vegetables: In a skillet, heat a little oil over medium heat. Add the sliced bell peppers and onion. Sauté for about 5 minutes until they start to soften.
7. Add Pineapple: Stir in the diced pineapple and cook for an additional 2-3 minutes until heated through.
8. Heat the Marinade: In a small saucepan, bring the reserved marinade to a boil. Reduce the heat and let it simmer for about 5 minutes until slightly thickened.
9. Combine: Once the chicken is cooked, place it on a serving platter and top it with the sautéed vegetables. Drizzle the thickened marinade over the dish.
10. Garnish: Sprinkle chopped green onions and sesame seeds on top for added flavor and presentation.

These steps will guide you in creating this amazing Polynesian Chicken effortlessly.