IT is such a simple idea, so plainly obvious that many Southerners can’t believe they didn’t think of it first: take the South’s trademark refreshment  sweet iced tea  and make it alcoholic.

That, essentially, was the recipe used by a South Carolina distillery last year to create a phenomenon. Its elixir, Firefly Sweet Tea Vodka, tastes almost exactly like the beloved sweet tea poured at generations of Southern family reunions, church meetings and picnics.

In just months, Firefly Distillery on Wadmalaw Island has expanded sales of its Sweet Tea Vodka to 40 states. Below the Mason-Dixon line, where fans are most rabid, the amber-brown liquor flows at colleges, bars and football games. Sweet Tea Vodka is 70 proof, a bit tamer than most vodkas, but the sweetness makes it seem even less potent. The daintiest drinkers can take shots without wincing (except, perhaps, from the sugar).