Whisk all ingredients together in a small pot until combined and cornstarch is dissolved. Bring to a boil and cook, stirring, for 2-3 minutes until thickened and glossy. Adjust seasoning as desired, adding more sugar for a sweeter sauce, salt or additional soy sauce for a saltier flavor, or more vinegar for a tangier sauce.
Let cool and serve just slightly warm or at room temperature. Store in the refrigerator, covered, for up to 5 days and return to room temperature before serving.
Replace water with 1/4 cup canned pineapple juice.