My boys like the Bulldog brand of Tonkatsu sauce. However, you can make your own homemade sauce by adding the following ingredients together; ½ cup Worcestershire sauce, ¼ cup sugar, ¼ cup soy sauce, ¼ cup ketchup, 1 tablespoon french yellow mustard, ½ teaspoon ground all spice and place in a little pot and heat over medium heat for about 10-15 minutes, cool and serve)