The restaurant at 2350 Commercial Way was closed and the car had been parked there for about half an hour, the manager told deputies.
Deputies found Eric M. Spevack, 26, of Spring Hill, passed out in the driver seat. The car was running and in drive, according to the report.
A deputy opened the door and turned off the ignition.
Spevack had bloodshot, watery eyes and slurred speech, the report said. He was arrested after a battery of sobriety exercises.
Spevack was taken to the Hernando County Jail, where breath tests showed a blood alcohol level of 0.163, roughly twice the amount at which Florida law presumes impairment, the report said.
Spevack was wearing a wrist band from an Irish pub in Tampa, according to the report.