Police said he ran away with the sandwich he ordered, along with the cash.
An employee said the man ordered a sandwich and told him he was waiting for someone to bring him money to the restaurant on 195 Malabar Rd., NW.
The man waited until another customer in the store left, police said. That's when he gave the employee a note and showed him the gun tucked in his waistband.
The suspect is a thin-built Asian male in his 20's, about six feet tall wearing a red polo shirt, black cap, black pants and slide-on sandals.
Brevard County Sheriff's Office and Palm Bay Police Department established a perimeter but could not find him.
Anyone with information, call Central Florida CRIMELINE at 1-800-423-TIPS.