Preheat oven to 375°F (190°C). Cut tops off peppers and remove seeds. Optionally blanch for 5–6 minutes. Place in baking dish.
Heat olive oil in skillet. Sauté garlic 1–2 minutes, then add shredded chicken, teriyaki sauce, pineapple, ginger, red pepper flakes, salt, and pepper. Cook 5–6 minutes. Stir in rice and combine well.
Fill each pepper with chicken and rice mixture, pressing down gently. Drizzle tops with olive oil.
Cover with foil and bake 25–30 minutes. For crispier tops, uncover for last 5 minutes.
If using, sprinkle cheese on top during final 5 minutes of baking and let melt.
Cool slightly before serving. Garnish with extra pineapple or green onions if desired.
