A bar in New Jersey had an unusual recipe for scotch: rubbing alcohol mixed with caramel food coloring. The discovery was made by police in “Operation Swill” -- a yearlong investigation into 29 bars that have been scheming their patrons.

The bars, which include 13 TGI Fridays, have been accused of using cheap liquor, dirty water and rubbing alcohol instead of premium booze customers ordered, AP reports. Police confiscated 1,000 open bottles of vodka, gin, rum, scotch, whiskey and tequila from the wells of the bars, according to a statement from the New Jersey Attorney General’s Office.

“This alleged scheme is a dishonest ruse to increase profits, and it is a slap in the face to the consumer,” Attorney General Jeffrey Chiesa said in a statement. “Consumers should have the peace of mind of knowing that they will get what they spent their hard-earned money on every single time -- no exceptions.”

The police learned of the illegal sales thanks to confidential informants, customer complaints and sample tests recovered by undercover police officers. The samples were tested using the True Spirit Authenticator -- a device that can quickly analyze what’s inside an alcoholic drink. Any samples that were flagged were sent to the drink manufacturers’ labs for further testing, The Record reports.

Penalties for serving a drink other than ordered range from a five-day suspension for the first offense to a 15-day suspension for the third offense. The bars could also face 30-day suspensions for “illegal activity on the licensed premise” and for not cooperating with the investigation.

The Briad Group, which owns the 13 TGI Fridays, says it will be conducting its own investigation.

"We want every assurance possible that our guests can continue to feel confident in the great food and drink they order at our T.G.I. Friday's restaurants," Rick Barbrick, president of The Briad Restaurant Group, told AP.

Below is a complete list of the New Jersey bars targeted in Operation Swill:

Railroad Café, East Rutherford    

The Brick House, Wycoff    

Sunset Tavern, Burlington    

Graziano’s Ristorante, Chesilhurst    

Villari’s Lakeside, Gloucester Township    

Yesterdays, Marmora    

TGI Fridays, West Orange    

Italian Affair, Glassboro    

Bells Tavern, Lambertville    

TGI Fridays, East Windsor    

Brunswick Grove, East Brunswick    

TGI Fridays, Old Bridge    

TGI Fridays, North Brunswick    

TGI Fridays, Piscataway    

TGI Fridays, Freehold    

TGI Fridays, Marlboro    

TGI Fridays, Hazlet    

Murray’s, Dover    

TGI Fridays, East Hanover    

Sona Thirteen, Morristown    

Blackthorn Restaurant, Parsippany    

Ruby Tuesday, Bridgewater    

TGI Fridays, Linden    

Café 34, Matawan    

Applebee’s, Kearny    

Cucina Calandara, Fairfield    

TGI Fridays, Hamilton    

TGI Fridays, Springfield    

TGI Fridays, Clifton