In a large bowl, combine the sour cream, mayonnaise, mustard, and horseradish. Stir that with a rubber spatula until it is thoroughly combined and there are no streaks.

To the bowl add the sugar, onion, and ranch dip packet, and again stir until thoroughly combined. Cover and store in the refrigerator for at least 30 minutes or until ready to serve. Serve with your favorite soft or crunchy pretzels for dipping!