It's called Smash Burger Sauce because it's a smashing good sauce to serve with homemade smash burgers and regular hamburgers! While there isn't a standard recipe for this classic burger sauce, it often consists of mayonnaise, ketchup, mustard, diced pickles, sweet pickle relish or lemon juice. The exact ratio of the ingredients can vary depending on personal preference. Other variations can include the addition of Worcestershire sauce, hot sauce, cayenne pepper, garlic powder and apple cider vinegar.