Not-so-happy hour.

A round of margaritas turned into a nightmare at a North Carolina Chili’s when bartenders mistakenly mixed a cleaning chemical into customers’ drinks — leaving three customers with chemical burns.

The mix-up happened Wednesday at the restaurant chain’s Forest City location, when an employee preparing the bar for lunch service mistook a granulated degreaser for sugar.

The chemical had been brought to the dining chain two days earlier by a worker who received it from a contractor power-washing the building’s exterior, according to the Foothills Health District.

The substance was placed in an unlabeled container and left in the bar area, where another employee found it Wednesday and mistook it for sugar while preparing margaritas.

Three customers ordered the cocktails and “immediately experienced discomfort,” suffering chemical burns in and around their mouths, the health agency said.

The patrons alerted the restaurant staff before leaving to seek medical attention.

Two employees then tasted the mystery substance in the container and developed similar symptoms.

“I’m not sure what degree of chemical burns they had, but they went to urgent care and were treated there,” Foothills Health District spokesperson Megan Rollins said, according to ABC News13.

The bizarre incident has left at least one regular customer shaken and questioning whether he will return to the restaurant’s bar.

“I was beyond surprised and almost scared,” Chili’s regular Levonne Baker told the outlet.

Baker compared the ordeal to something out of a horror movie.

“It has made me a little nervous about going back to the bar because it’s like what’s in there next? I mean, am I going to be the next person who’s going next door? And not for an oil change,” he said.

A mechanic and an urgent care facility are located next door to the Chili’s.

The Foothills Health District launched an investigation and immediately suspended the restaurant’s food service permit, ordering staff to thoroughly wash and sanitize affected food preparation areas, equipment and surfaces.

The permit was reinstated by Thursday morning after environmental health specialists completed their investigation and determined the restaurant met “all applicable food safety requirements.”

“This incident highlights the importance of proper chemical labeling, storage, and handling in food service establishments, as required by the North Carolina Food Code, to prevent chemical contamination and protect public health,” Foothills Health District Director Jason Masters said.