Preheat oven to 375°F. Cut tops off peppers, remove seeds and membranes, then arrange upright in a 9x13-inch baking dish.

Heat 1 tablespoon olive oil in a large skillet over medium heat. Add garlic and cook 1 minute until fragrant. Stir in chicken, teriyaki sauce, pineapple, ginger, and red pepper flakes. Cook 5 minutes, stirring occasionally.

Remove from heat and fold in cooked rice until evenly coated. Adjust salt and pepper.

Spoon filling into each pepper, packing it down gently. Drizzle remaining olive oil over the tops.

Cover dish with foil and bake 25-30 minutes until peppers are tender. Remove foil last 5 minutes for crispier edges. If using cheese, add it during final 5 minutes until melted and bubbly.