SexBurger is a corporation owned by Fizzco. Like all Fizzco-related things, SexBurger produces food and beverages.
The restaurant's purpose was to cater to the low self-esteemed. It always promised a free side of "sex appeal" with every purchase.
Seeing as how SexBurger was owned by Fizzco, it is likely that OverCharge Delirium XT was sold here. This may have added to the overall mutant-count in Sunset City.