Preheat the air fryer to 400 degrees Fahrenheit (200 degrees Celsius).
In a large mixing bowl, toss the halved Brussels sprouts with olive oil, salt, and black pepper until evenly coated.
Place the Brussels sprouts into the air fryer basket in a single layer and cook for 8 minutes.
While the sprouts cook, whisk together the sweet chili sauce, soy sauce, and garlic powder in a separate bowl.
Toss the chicken cubes in the sauce mixture until fully coated, reserving 2 tablespoons of sauce for finishing.
Add the chicken cubes to the air fryer basket with the Brussels sprouts, ensuring they are spread out for even cooking.
Air fry the chicken and sprouts together for 7 to 10 minutes, shaking the basket halfway through, until chicken reaches an internal temperature of 165 degrees Fahrenheit (74 degrees Celsius).
Remove from the air fryer, toss with the reserved sauce, and garnish with sesame seeds and green onions before serving.