"Special sauce" was the garnish used on Dexter Jettster's sliders, one of the specialties at Dex's Diner. It was also called "slider garnish."
Patrons were known for ordering as much as a liter of it, with nothing else. When Jettster owned the diner, some of the customers accused him of adding addictive drugs to the sauce.
Dex always meant to find the time to bottle his wildly popular sauce and make his fortune, but he never got around to finding that elusive "minute away from the stove."