Which of these soda brands was the rival on the "Pepsi Challenge"?

Even though Pepsi and Coca-Cola had been competing for market share since the birth of Pepsi-Cola in 1899, the Pepsi Challenge marked a turning point in the Cola War. The blind taste test found that more people liked the taste of Pepsi than Coke. In response to the test, Coca-Cola would reformulate its cola and launched New Coke, which was an utter disaster. Pepsi sales would benefit from the New Coke mishap for some time, but then Pepsi started making mistakes of its own.

Source: Business Insider