Toss the chicken pieces in cornstarch until lightly coated. This helps create a slight crust and thickens the sauce later.
Heat oil in a large skillet or wok over medium-high heat. Add the chicken in a single layer and cook until browned on all sides, about 5–6 minutes. Remove and set aside.
In the same skillet, add a bit more oil if needed. Sauté minced garlic and ginger for about 30 seconds until fragrant.
In a bowl, whisk together bourbon (or apple juice), soy sauce, brown sugar, ketchup, apple cider vinegar, crushed red pepper flakes, and water. Pour the sauce into the skillet with the garlic and ginger.
Return the chicken to the pan and stir to coat. Bring the sauce to a simmer, then reduce the heat and cook for 8–10 minutes, stirring occasionally, until the sauce thickens and the chicken is cooked through.
Serve hot over rice, noodles, or steamed vegetables. Garnish with green onions or sesame seeds if desired.