Preheat oven to 400°F and spray a 9x13-inch baking dish with cooking spray.
Place the cubed chicken in the prepared baking dish.
In a medium bowl, whisk together soy sauce, hoisin sauce, rice vinegar, honey, cornstarch, garlic, ginger, sesame oil, and red pepper flakes until smooth.
Pour the sauce over the chicken and toss to coat evenly.
Bake uncovered for 30-35 minutes, stirring once halfway through, until chicken is cooked through and sauce has thickened.
Sprinkle with sliced green onions and sesame seeds before serving over steamed rice.