Place mayonnaise, sugar, creamed horseradish, and salt in a small bowl.
Stir until well combined.
Cover and place the sauce in the refrigerator for at least 1 hour prior to serving. For optimal flavor, refrigerate the sauce overnight.
Notes
Note: Creamy horseradish is usually available in the condiment section of the grocery store, will be more like the the true Arby's horsey sauce, but fresh works.
Nutrition - See Recipe Post for Nutrition Disclaimer