When I was riding on the city squads, most of our daytime calls were at grocery stores and restaurants.
Each one of us had a list of restaurants we would not go to eat. Deep down we knew that all restaurants were the same, but not making a call on a specific restaurant gave us plausible deny-ability.
It is a good thing the human digestion system is as strong as it is and can handle massive amounts of bacteria.
So fast food or traditional joint. They are all filthy.
At least with fast food, there is a good chance the food is not left laying as long as it is in a more traditional place.