Where would the classic roast beef sandwich be without horseradish? Just an ordinary sandwich, I guess. There is nothing like a good dose of horseradish sauce to adding a bit of a kick to appetizers, meats, and sauces. It has also been known to clear up those sinuses! So, just what exactly is in this spicy sauce? Well, it is very simple: grated horseradish root mixed with vinegar. Available here are prepared sauces from Heinz, Kraft, Sara Lee, and more. All are full of flavor and contain just the right amount of bite.