"We are working with the police in their investigation right now", Shake Shack tweeted.
The three officers are now being treated at the hospital and expected to recover.
They were all transported to a local hospital for treatment and were fortunately not "seriously harmed", police said.
The incident occurred on the evening of June 15 when the three officers went to a Shake Shack restaurant in Lower Manhattan when, at some point during their meal, they began to feel sick while drinking their milkshakes.
Among those injured was Sgt. William Maher, who was struck by an SUV and was hospitalized for several days, police said.
"After a thorough investigation by the NYPD's Manhattan South investigators, it has been determined that there was no criminality by shake shack's employees", the department's Chief of Detectives Rodney Harrison said in a statement early Tuesday.
"When New York City police officers can not even take (a) meal without coming under attack, it is clear that (the) environment in which we work has deteriorated to a critical level", the union said.
Trump to sign executive order
The order will encourage "police departments nationwide to adopt the highest professional standards to serve their communities". On Monday, the president told reporters the order would help preserve "law and order", and "justice" and "safety".
The NYPD will still have plainclothes officers among the ranks, Mr Shea said. He said the officers discovered the substance and did not finish their drinks but had already ingested some of the tainted substance.
Like most U.S. cities, NY has had daily protests demanding racial justice since the May 25 killing of Floyd, a black man, by a white Minneapolis officer. She also believes the surge of released inmates across the country due to coronavirus is stifling productive conversations about sensible law enforcement reform.
Police reform has become a rallying cry not only in the United States but across the world after George Floyd, a 46-year-old Black man, died while a white police officer placed a knee on his neck for nearly nine minutes in a bid to restrain him.
"We can not afford to let out guard down for even a moment", Lynch warned.
Shea said it was a policy shift and no reflection of the officers.
"Shooting and murders are both climbing steadily upward, but our city leaders have clearly decided that proactive policing isn't a priority anymore", Police Benevolent Association president Pat Lynch said in a statement.