The Pepsi Challenge has been an ongoing marketing promotion run by PepsiCo for the last decade. The challenge is designed to be a direct response to critics who allege that Coca Cola and Pepsi Cola are identical drinks, with no meaningful differences. The challenge takes the form of a taste test. At malls, shopping centers and other public locations, a Pepsi representative sets up a table with two blank cups, one containing Pepsi and one with Coke. Shoppers are encouraged to taste both colas, and correctly identify which is Pepsi and which is Coke. If they can correctly identify the two, they win a prize. The implication is that Pepsi tastes better than Coke, and thus its distinct flavor can be easily identified in a side-by-side challenge.
Referenced in Pulp Fiction, an excellent movie.
"Excuse me sir, would you like to try the 'Pepsi Challenge'?"
"sure, why not....hey, what the fuck? These taste exactly the same!"