Fast food was a type of food that was made and sold quickly.
When the Cold began their attack on humanity on 2 April 1963, Susan Foreman and some others took cover in a Wimpy Bar. They lived on hamburger buns with ketchup, frozen burgers being the next option. (PROSE: Time and Relative)
In Perivale, Ace worked at a fast food chain where she encountered the Ergon. Mistaking it for her friend Barry Groves in a chicken costume, Ace gave the Ergon a box of fries, which it returned to its master Omega in the anti-matter universe. (PROSE: Anti-Matter with Fries)
Ace and Hex hoped to find a McDonald's when the TARDIS landed in what was apparently London. (PROSE: Six Impossible Things Before Breakfast)
The Tenth Doctor accidentally called Pizza Geronimo in place of UNIT due to their numbers being almost identical. (TV: Planet of the Dead)
McLintock's Candy Burgers sponsored Vator Verse aboard Starship UK in the 33rd century. (TV: The Beast Below)
Torchwood Three often got food from the Cardiff branch of Jubilee Pizza, which had an account in the name of "Torchwood", courtesy of Owen Harper. (TV: Everything Changes)
Ryan Sinclair had an appetite for fast food, but considered spray cheese to be a "step too far." (PROSE: Gatecrashers)