This is a comment from the rate the cop post below, it earned a place as its own post… enjoy!
If you want to find all the cops
They’re hanging out in the donut shop
“Walk Like An Egyptian”, The Bangles
“So I heard that Southland Corporation found a way to guarantee that 7-11s would never get robbed. They started selling donuts. That’s when I said, ‘There goes the neighborhood’.”
In fiction, it’s much more probable that you’ll see a cop eating a donut than anyone else, except for Homer Simpson. The cop guarding your jail cell will be dunking their donut with pink frosting in their cup of coffee. The cop in the stakeout will have a half-empty box of donuts in their car. When taking a break from driving, they’re hanging out at the donut shop.
In more humorous displays, the cop might react to a donut as Scooby Doo would to a scooby snack. It might be the reason for them to have joined the force. Heck, in fact, “Officer Donut” is a casual insult for a cop.
The reasons for this are actually not all insulting. Cops will usually consume lots of coffee, because it’s necessary for them to stay awake during the night, and the donut is usually a sweet to dunk in the coffee or to remove its sour aftertaste. Donuts are also ready-made and stored in boxes – a good food to store in patrol cars for a long time, as they don’t melt or get inedible when old. They also tend to be both filling and cheap, and as Donut Shops tend to open early, for a while they were among the few places open for someone working the graveyard shift. Donut shops also tend to give out free donuts to law enforcement.
As donuts are fattening sweets, the cop munching them will usually be a fat, lazy, moustached Obstructive Bureaucrat. (Strangely, they never get glaze or frosting in their mustache…)
As for corrupt cops, just remember that Evil Tastes Good – as do donuts.
While this might be Truth In Television, it could probably be seen today as an Evolving Trope. If anything, a cop might be hesitant in buying donuts because of the inevitable stigma associated with them. On the other hand, The Red Stapler effect comes into play. On their first round, a rookie might buy some donuts, believing all cops love them.
It should be noted that this is primary an American/Canadian based trope as donuts are nowhere near as popular with the police in many other countries.