In a medium saucepan, combine soy sauce, rice vinegar, brown sugar, hoisin sauce, chili garlic sauce, sesame oil, garlic, and ginger.
Whisk the mixture over medium heat until it begins to simmer and the sugar is fully dissolved.
In a small bowl, mix the cornstarch with water to create a slurry.
Slowly pour the slurry into the simmering sauce while whisking constantly to avoid lumps.
Continue cooking and stirring until the sauce thickens to your desired consistency (about 2–3 minutes).
Taste and adjust heat level with more sriracha if desired.
Remove from heat, let it cool, and store in a glass jar. Refrigerate for up to 1 week.