Phrase(s): rustle something up Rur. to manage to prepare a meal, perhaps on short notice. • I think I can rustle something up for dinner. • Please rustle up something to eat.
McGrawhill's American Idioms And Phrasal Verbs
Get together food or some other needed item with some effort, as in I don't know what we have but I'll rustle up a meal somehow, or You boys need to rustle up some wood for a campfire. The verb rustle here means "to assemble in a hurry." [Late 1800s]
American Heritage Idioms