Bring chicken stock to a boil. Add ginger and soy sauce and mix well. Let cook for 5 minutes. Turn off heat.
In 4 soup bowls add bean sprouts, mushrooms, scallions and spinach. Pour stock on top. Let sit for 1 minute and serve.
Make sure not to add salt until the end if needed (because the soy sauce adds salt and you probably already added salt to the soup originally). You can use store-bought chicken stock for this, but of course it’s not the same!