Preheat the oven to 425°F (220°C) and line a baking sheet with foil or parchment if desired.
Prepare the sauce by whisking together soy sauce, sweet chili sauce, sriracha (if using), minced garlic, and cornstarch in a small bowl until smooth; stir in sesame seeds if using.
Place the cut chicken, broccoli florets, chopped bell pepper, and snap peas on the prepared baking sheet in a single layer.
Drizzle the sauce evenly over the chicken and vegetables and toss gently on the sheet with a spatula or tongs to coat.
Bake for about 20 minutes, until the chicken is cooked through and vegetables are crisp-tender, stirring once halfway through if needed for even cooking.
Divide among 4 plates or meal-prep containers and serve with rice or noodles if desired.
