Manhattan Special, founded by Ms. Passaro's great-grandmother in 1895 and still operating out of its original plant in Williamsburg, Brooklyn, may not be familiar to people outside the New York metropolitan area. But generations of New Yorkers have grown up with it, and it remains a strong seller in New York, Connecticut and New Jersey. It is one of a surprising number of older regional soda pop brands — including Moxie in New England, Cheerwine and Blenheim in the Carolinas, Vernors and Faygo in Detroit, Buffalo Rock in Alabama, Big Red in Texas, Ale-8-One in Kentucky, Apple Beer in Utah, Bubble Up on the West Coast, and Green River in the Midwest — that have limited distribution and no national profile but remain popular on their home turf.

Think of these regional sodas as a sort of effervescent subculture, bubbling under the surface of the ruthlessly consolidated soda market. The trade journal Beverage Digest said that last year more than 90 percent of the $63 billion soda category was controlled by the industry's big three: Coca-Cola, whose brands include Sprite and Barq's root beer; Pepsi-Cola, whose stable features Mountain Dew and Slice; and Cadbury Schweppes, which owns Dr Pepper and 7Up. Throw in these bottlers' distribution muscle and control over retail shelf space, and the regionals face long odds.