Taco Bell decided to start serving alcohol at certain locations because people were already adding booze to their drinks

Taco Bell's decision back in 2015 to start serving alcohol at some locations seemed like a bold choice for a fast-food chain.

However, according to one executive, the chain was just helping out customers who were already acting as DIY bartenders.

"People would come through on drive-thru and say, 'could you please leave a little off the top,'" Taco Bell COO Mike Grams told Business Insider. "And we'd know exactly what they meant."

So when Taco Bell leaders were spitballing about potential innovations prior to launching the chain's sit down-centric Cantina brand in 2015 and someone mentioned serving booze, it just made sense.

At one time, the fast-food chain might have decided to shut down the somewhat radical idea. However, Grams said that the drive to keep things fresh at Taco Bell - and executives' reliance on managers for info on what customers actually want - convinced the chain to give booze a try. 

There are currently only seven Taco Bell Cantina locations in the US, though the chain has plans to open four more by the end of 2017. The locations feature trendy decor, DJs blasting music, and tapas style appetizers. All serve at least one local beer.

However, the pièce de résistance of the drinks menu is the beverage that customers created themselves - Twisted Freezes with a shot of rum, tequila or vodka. 

Still, Taco Bell lovers should know that there's one thing that the Cantina locations won't be serving. 

"You can't go on in there and get a shot," Grams said. "We're not doing bars."