The World's Largest Sandwich was a small stand seen in Lilo & Stitch: The Series. It contains a humongous submarine sandwich inside.
In "Shortstuff", Gantu and Reuben are seen together at an amusement park. Gantu is searching for Experiment 297 (Shortstuff). Reuben suddenly notices an enormous submarine sandwich inside a small stand titled "World's Largest Sandwich." He then eagerly approaches the giant sandwich and attempts to eat it, only to be stopped by Gantu who tells him that they did not come here to eat, but they were after an experiment.
Later, Gantu somehow gets a hold of Jumba's protoplasmic growth ray and enlarges Reuben into a giant behemoth. Gantu then commands the humongous Reuben to squash Lilo, Stitch, Jumba and Pleakley below him. However, Reuben instead trudges over to the deliciously huge sandwich. Gantu scolds Reuben and tells him that he missed, but Reuben replies that he never misses. He then seizes the giant sandwich and devours it while sitting on top of Gantu, much to the latter's discouragement and humiliation.