Slice the chicken breast into thin strips and coat with cornstarch.
Heat the vegetable oil in a large skillet over medium-high heat.
Cook the chicken strips in the skillet for 5-7 minutes until golden brown, stirring occasionally.
Remove the chicken and sauté garlic and ginger in the same skillet for 30 seconds.
Add soy sauce, water, and brown sugar to the skillet and stir well.
Mix cornstarch with water to create a slurry and add to the sauce to thicken.
Return chicken to the skillet, add sesame oil and sriracha, and toss to coat.
Garnish with green onions and serve over rice or noodles.