Heat vegetable oil in a wok or large skillet over medium-high heat.
Add minced garlic and grated ginger to the hot oil, sautéing for about 30 seconds until fragrant.
Add the marinated chicken to the wok, stir-frying until it is browned and cooked through.
Incorporate sliced green onions into the stir-fry, cooking for an additional minute.
In a small bowl, whisk together soy sauce, hoisin sauce, water, brown sugar, and rice vinegar. Pour this sauce mixture over the chicken, stirring to coat evenly.
Drizzle the cornstarch slurry into the wok, continuing to stir until the sauce thickens.