In a small mixing bowl, whisk together brown sugar, buffalo sauce, water, apple cider vinegar, and cornstarch until smooth. Set aside.

Trim and cut chicken breasts into 1-inch bite-sized pieces. Combine with garlic powder, salt, and pepper in a separate bowl. Toss with cornstarch until evenly coated.

Heat olive oil in a large skillet over medium-high heat. Add half of the chicken and cook for 4–7 minutes until golden brown and cooked through. Transfer to a plate and repeat with remaining chicken.

In the same skillet, add remaining olive oil and first batch of chicken. Pour in prepared sauce, stirring constantly for 30 seconds to 1 minute until thickened.

Serve the Firecracker Chicken immediately over rice or noodles, garnishing with chopped scallions if desired.