Fried rice sauce is straightforward but essential to a good chicken fried rice: mix soy sauce, oyster sauce, mirin or Shaoxing wine, sugar, and toasted sesame oil. If you cannot find Shaoxing wine, you can use mirin. The flavor is slightly different, and mirin is a bit sweeter, so you may have to cut the sugar. You can also add a touch of fish sauce. Regardless, ensure you constantly taste the rice sauce and adjust it as needed to not have an overly salty or sweet sauce for your rice.