Cheap brewed coffee from convenience stores is giving Starbucks a run for its money as the recession continues to bite.

CU, GS25 and 7-Eleven sold a combined 9.58 million cups of brewed coffee last month, or 320,000 cups a day, which is similar to Starbucks' average daily sales in Korea. 7-Eleven was the first to launch brewed coffee early in 2015, and less than two years later convenience stores have surpassed 10 percent of the overall market of 3 million cups a day.

The coffee is hardly top-of-the-range and the cups are small, but the cheap Arabica beans pack a powerful punch and cost little more than a cup of instant coffee.

"We started off by selling brewed coffee in 20 stores," says Ham Tae-young at 7-Eleven. "Now we sell it in 4,200 or half of our stores, and it's overtaken soju as our best-selling product."

GS25 and CU jumped on the bandwagon in December 2015 and sales have grown two- to threefold already.

