Preheat your oven to 400°F (200°C). Lightly grease a large sheet pan or line it with parchment paper for easier cleanup. Make sure the pan is large enough so the ingredients roast instead of steam.
Cut the chicken into bite-sized pieces so they cook evenly. Chop the peppers into similar-sized pieces and slice the onion into wedges. Cut fresh pineapple into chunks if you're not using pre-cut fruit.
In a mixing bowl, whisk together soy sauce, honey, ketchup, garlic, ginger, rice vinegar, sesame oil, and black pepper. Stir until the ingredients are fully combined and the honey has dissolved.
Mix the cornstarch with water in a small bowl until smooth. Add this mixture to the sauce and whisk again. This helps create a glossy coating while everything roasts.
Place the chicken pieces into a large bowl and pour about half of the prepared sauce over them. Toss everything until each piece is evenly coated. Let it sit for a few minutes while preparing the vegetables.
Spread the chicken, peppers, onion, and pineapple evenly across the prepared baking sheet. Avoid overcrowding because the ingredients need space to roast properly instead of releasing too much moisture.
Drizzle olive oil over the vegetables and pour the remaining sauce across the entire pan. Toss gently to coat everything without breaking the pineapple pieces.
Bake for about 15 minutes, then carefully remove the pan and stir the ingredients. Return it to the oven and continue baking for another 12–15 minutes until the chicken reaches an internal temperature of 165°F.
If you'd like slightly browned edges, switch the oven to broil for 2–3 minutes. Watch carefully because the honey can caramelize quickly and may burn if left too long.
Remove the pan from the oven and let it rest for a few minutes. Sprinkle chopped green onions and sesame seeds over the top before serving. Enjoy it with steamed rice, brown rice, or your favorite side dish.