NEW YORK (CNN/Money) - The beverage aisle is about to get more crowded as Pepsi and Coca-Cola debut new diet colas.

Coca-Cola is adding a fourth diet cola to its line this June with Coca-Cola Zero, with no calories, the company announced Tuesday. And this spring Pepsi is relaunching its one-calorie Pepsi ONE with Splenda sweetener rather than aspartame.

Reformulated Pepsi One, available on shelves and coolers in late March, is part of Pepsi's focus on diet soft drinks this year, said Katie Lacey, Pepsi-Cola North America's vice president of carbonated beverages, in a statement.

While for Coke, "Coca-Cola Zero is exactly what young adults told us they wanted," said Dan Dillon, vice president, Diet Portfolio, Coca-Cola North America, in a statement.

Apparently America's youth wanted a cola sweetened with sugar subsaspartame and acesulfame potassium. The new cola will not replace Diet Coke, favored by a different group of cola swiggers, according to the company.

Both Pepsi's (up $0.08 to $52.64, Research) and Coke's (up $0.06 to $41.66, Research) new diet brews are aimed young adults, mostly male, according to Adage.com. Apparently, more men are gulping reduced-calorie and zero-calorie beverages to stay trim, the article says.

Along with Diet Coke and the new Zero, Coke's diet selection includes a Splenda-sweetened Diet Coke, Diet Coke with lime and C2, launched last year.

For the curious, Coca-Cola Zero will auction off a sample pack of the cola on eBay in April, and the proceeds will be donated to charity.