PepsiVanilla has a sugar-free version, DietPepsiVanilla, which hit supermarket shelves almost instantly after PepsiVanilla was released, to act as a competitor of DietVanilla Coke.
Vanilla is a flavouring, in its pure form known as vanillin, derived from orchids in the genus Vanilla.
Other regions where Pepsi outsells Coke are in central Appalachia, the state of North Dakota, the predominantly Mormon region in and around the state of Utah (the Mormon church has stock in Pepsi), and the city of Buffalo (by a 2-1 margin), all in the United States.
Industry analysts credit Vanilla Coke's launch last year as a huge success for Coke, similar to Pepsi's breakthrough in 2001 with Mountain Dew Code Red, a cherry-flavored variation of the drink.
Pepsi's North America volume grew 4 percent for the quarter, led by a better performance from its Mountain Dew and DietPepsi brands, although its trademark Pepsi brand disappointed.
Pepsi last year replaced Spears with Beyonce Knowles, lead singer of pop group Destiny's Child, as its latest celebrity endorser.