the most relevant brand is Arby's....
Arby's does things a little differently. According to an Arby's employee on a 2021 Reddit thread discussing the fast food items people should never order, the chain's sandwiches are made with "a compressed block of beef scraps." They went on to say that the block of scraps comes sitting in a bag of beef broth and is warmed under a lamp until it's ready to be served.
Jim Lowder, a Quality Assurance representative for Arby's, told Snopes in 2005 that the roast beef "consists entirely of Beef and a Self-Basting solution, which contains just enough water to keep the product juicy throughout our restaurants' 3-hour roasting process and during slicing." Whether that grosses you out or not, it's always good to know exactly where your food is coming from.