First came vitamin-enhanced water, then açai juice. Is coconut water the next big health-drink fad? Michael Kirban and Ira Liran sure hope so. The pair, friends from college, got the idea to sell coconut water after they learned about the drink from two young Brazilian women they met at a bar in New York City in 2003. (Liran eventually married one of them.) Today, Kirban and Liran's company, Vita Coco, controls nearly 70 percent of the $30 million -- and growing -- U.S. market for coconut water.

Not long ago, coconut water was all but unheard of in the U.S. Now, Vita Coco has some stiff competition. Zico, a Hermosa Beach, California, company launched in 2004, counts Coca-Cola as a backer. And Pepsi recently acquired Brazilian coconut-water maker Amacoco.

One retailer Kirban and Liran approached early on declared Vita Coco tasted like "sock water." But today, 12,000 retail locations, including many Whole Foods and Safeway outlets, sell the electrolyte-rich drink, which is promoted as a sort of natural Gatorade. Vita Coco's revenue climbed from $8 million in 2008 to more than $20 million in 2009. "People really get hooked on this stuff," says Kirban.