In a medium saucepan, combine water, soy sauce, honey, sriracha, and minced garlic. Set the saucepan over medium heat and bring the mixture to a boil, stirring occasionally. In a small dish, stir together 2 tablespoons of cornstarch and 2 tablespoons of cold water until dissolved. Pour the cornstarch slurry into the saucepan and stir until the sauce thickens. Reduce the heat to low. Add the chicken pieces into a large zip-top bag and sprinkle the top with cornstarch. Seal the bag and toss the chicken inside until evenly coated with cornstarch. Set a large non-stick pan over medium heat and lightly coat the bottom with oil. Add the chicken in a single layer and sauté for a few minutes on each side until cooked through. Avoid crowding the pan and cook in batches or use two skillets to speed up the process. Once the chicken is cooked, turn off the heat. Pour the sauce over the chicken and stir to coat. Season with salt and pepper to taste, if needed. Serve over white rice, if desired, and garnish with sesame seeds and sliced green onions.