- In a medium-sized pot, combine the water, vinegar, soy sauce, and Worcestershire sauce over medium heat. Stir to mix. 
- Add the brown sugar, mustard powder, turmeric, garlic powder, cumin, and black pepper to the pot. Stir continuously until the sugar dissolves and the ingredients are fully combined. 
- Allow the mixture to come to a gentle simmer. Let it cook for about 5 minutes, stirring occasionally to prevent burning. 
- Remove the sauce from the heat and let it cool. Once cooled, stir in the cilantro (if using). 
- Transfer the sauce to a glass jar or bottle and store in the refrigerator for up to 2 weeks.