Fast Food Ice: Ice and soda machines are, apparently, very hard to keep clean. The Reddit thread contains horror stories of mold and other things we won't go into here. If you're concerned about the state of what you're drinking, you probably shouldn't order soda at a fast food restaurant.
Chicken Nuggets: The quality of this fast-food favorite obviously depends on the restaurant in question, but chicken nuggets, and what exactly they're made of, seem to be an item of concern across the board. Unconventional Pizza Toppings: The bottom line seems to be that topping meats and "'quirky' toppings such as green olives, meatballs, spinach, artichokes, sauerkraut, sun-dried tomatoes, etc." are rarely fresh.
Sweetened Teas: This drink makes the list not for food hygiene concerns, but purely for the amount of sugar that goes into sweetened tea recipes. Fast food workers want you to know that sweetened teas are comparable to any soda and are definitely not a healthy option.
Ketchup bottles and salt and pepper shakers at some restaurants are often re-filled again and again without ever being cleaned. Short story? Stay away.