Soy Sauce with Lime Juice (Best Option)
1 tablespoon soy sauce + 1 teaspoon lime juice per 1 tablespoon fish sauceSoy sauce contains glutamates that provide umami similar to fish sauce, while lime juice adds the bright acidity that fish sauce imparts. Together, they simulate the salty, tangy, and savory profile essential for soup.
For best results, add lime juice gradually and taste to avoid overpowering acidity. Use low-sodium soy sauce if saltiness is a concern. Stir well to ensure even flavor distribution.
This substitute maintains the liquid consistency and depth of flavor, resulting in a soup that closely resembles the original taste, though it lacks the subtle marine notes of fish sauce.