The convenience store has celebrated its name day with free Slurpees since 2002 but this year served up a special birthday cake flavor honoring its signature drink's 50th anniversary.
7-Eleven offered small Slurpees to all customers from 11 a.m. to 7 p.m.
More than 500 Slurpees had been distributed at River Edge's Kinderkamack Road as of 5:30 p.m., cashier Drew Fay said.
"We assembled them a day in advance and we're still trying to assemble more," he said.
Hackensack's Main Street store owner Rama Hemadri had given out 1,500, he said.
The 7-Eleven on Clifton Avenue in Clifton ran out of free cups at 6:30 p.m., manager Nadia Sawlahi said.
"It's been crazy," she said. "The lines were out the door. We went through three boxes of cups."
Email Anthony Locicero to submit photos.
Click here to follow Daily Voice Garfield-Lodi and receive free news updates.