Basically, Pepsi introduced a soda called Crystal Clear that was gaining momentum in the "clear soda" market. Coke wanted to sabotage the public perception, so they introduced "Tab Clear" and made it taste so terrible, that both products failed within 6 months. After that, no one wanted to touch clear soda for a while. (That is, until Coke reintroduced another drink called Sprite).

[1]http://thedailyjournalist.com/pen-and-pad/corporate-sabotage...