Combine 1/4 cup water, rice vinegar, and sugar in a pot over medium-high heat.

Bring the mixture to a boil, then add minced garlic and crushed red pepper flakes.

Reduce heat to a simmer and cook for a couple of minutes to infuse flavors.

Add sriracha and fresh ginger (if using).

In a small bowl, dissolve cornstarch in 1 tablespoon of water.

Bring the sauce back to a low boil.

Add salt and the cornstarch/water mixture.

Stir constantly until the sauce reaches desired thickness, about 3-5 minutes.

Let the sauce cool before using as a dipping sauce or storing in the refrigerator.