While most Americans know soy sauce as a salty topping that accompanies Asian foods, in many parts of the world, it's a central ingredient of virtually every meal. It comes in numerous varieties, including light, low-sodium and citrus, each of which is interchangeable with the other. However, if there isn't a drop of soy sauce to be found in your home, there are several substitutions you can make to create a similar taste and feel.
Soy sauce has one of the highest sodium contents of any condiment, so if you need some in a pinch, just use salt. To get the most authentic taste, mix 3/4 teaspoon kosher salt and 1/2 teaspoon granulated sugar, and dissolve the combination in 1 tablespoon hot water. The flavor won't be as complex (and it won't look the same), but it will certainly do the trick [source: Joachim].
If you don't feel like pouring liquid salt onto your food, try using teriyaki sauce or kecap (a thick Indonesian soy sauce).