Stir water, sugar, ketchup, pineapple, vinegar, red pepper flakes, soy sauce, steak sauce, and hot sauce together in a saucepan over medium heat. Remove 1/2 cup of the sauce to a small bowl; whisk cornstarch into the sauce in the bowl. Bring the sauce in the saucepan to a boil, stir the sauce with the cornstarch into the boiling sauce. Cook, stirring occasionally, until thickened, about 15 minutes. Remove from heat and allow to cool slightly before using.
