​This was definitely not on the Dollar Menu.

A night shift manager at a Bronx McDonald’s was dishing up more than ​burgers and ​fries — he was busted for ​offering a side of cocaine in his Happy Meals.​

Authorities caught Frank Guerrero, 26, red-handed during a three-month undercover investigation dubbed “Operation Off the Menu,” according to the city’s Special Narcotics Prosecutor Bridget G. Brennan.

“The conduct was so blatant it would be comical if he weren’t committing a serious narcotics crime,” Brennan said. “Ordering coke took on an entirely different meaning on the night shift at this McDonald’s.”

Guerrero allegedly sold cops $10,900 worth of cocaine in eight separate sales out of the franchise at 1600 Bruckner Blvd. in the Soundview section of the Bronx.

Although the eatery only took late-night orders through the drive-through window, Guerrero allowed his drug customers to enter the main restaurant, officials said.

In one sale to an undercover at the counter, he allegedly concealed cocaine in a cookie bag, which he placed inside a larger McDonald’s order of two cheeseburgers, a soda and fries, authorities said. Other employees were milling about nearby.

On another occasion, Guerrero allegedly took a break from flipping burgers to sell $6,250 worth of cocaine to an undercover inside the fast-food chain’s public bathroom.

He had allegedly stashed the drugs inside the restroom’s soap dispenser earlier that day, officials said. The undercover then sat at a booth and ate a McDonald’s meal personally delivered by Guerrero.

Five other sales were conducted in the McDonald’s parking lot. Police surveillance allegedly revealed that Guerrero regularly sold cocaine to buyers during his shift.

Authorities executed a search warrant on his home in the Pelham section of the Bronx, where they allegedly seized 200 grams of cocaine and $5,300 in cash. Leidy Cabral Castillo and her 2-year-old child were inside the apartment at the time.

Guerrero, who had worked at McDonald’s for eight years, was arrested at 5 a.m. Wednesday while wrapping up his shift.

Guerrero and Cabral Castillo were expected to be arraigned Wednesday night in Manhattan Criminal Court on multiple counts of criminal possession of a controlled substance and unlawfully dealing with a child. He also faces numerous counts of criminal sale of a controlled substance.