Cops rarely pay for fast food on duty (well, some anyway). Most places will give it to them for free if they eat inside the store. Cheap security, and all that. I never got into the habit, and the practice is looked on more and more by police administrators as vaguely unethical.
CC
When I was young I had a buddy who worked at a McDonalds just off of the University of Pittsburgh campus.
They would give free coffee to City of Pittsburgh police officers. When the Pitt campus cops came in however he would tell them “no, the free coffee is for REAL cops!”
Hopefully he never did so much as jaywalk within the boundaries of the Pitt campus.