"Sorry for the inconvenience, but our team refuses to work for a company that treats their employees like sh*t when they have put everything into this story."
It is signed off by the "ex-Sonic crew" with a final "F**K YOU" to the new owners.
Similar mass resignation protests have also taken place at Sonic restaurants in other Ohio locations, including Grove City and Lancaster.
In Lancaster, signs saying "Goodbye" and "Thank you, next" have also been hung up, while a printed email from staff to the new owners has also been displayed, which describes the business as "the most trashiest company we have ever seen".
Sonic, a drive-in fast-food restaurant chain, was founded in 1953 and specialises in classic American fare such as fries, burgers and hot dogs.
There are more than 3600 Sonic restaurants across America, although it is believed the current crisis is only affecting certain stores and not the entire company.
According to the Scioto Post, the stoush began after the affected branches suddenly changed hands after being sold to SRI Operating Company, a management company connected with Sonic which runs franchises across the US.
That ownership change allegedly led to staff being laid off, as well as wages being cut from minimum wage to just US$4 ($5.80) per hour plus tips.
"Circleville, Lancaster, and Grove City crews have all walked out and quit after the franchise was bought out by corporate," an anonymous source told the publication.
"The regional director, two district managers and four general managers have all been let go. All of which have been working for the company in management for 7+ years."
Twitter users have been quick to throw their support behind the ex-employees, with many praising them for taking such a bold stand.
"They cut workers pay from min wage to US$4.00 + tips. US$4.00. Plus tips. TIPS. AT A FAST FOOD JOINT," one Twitter user posted, while another wrote: "I like Sonic, but I love this letter. It gives me so much hope to see workers supporting each other with bold actions like this. Best of luck to everyone involved."
Several former Sonic workers also chimed in, with one confirming it was a "horrible company to work for".
Sonic communications manager Kyle Lankford denied claims wages had been cut in a statement to VICE'S food website MUNCHIES.
"No wage rates at any level have decreased in this transition," he said.
"Of course, Sonic carhops often receive tips in addition to their wages."
