A popular Halloween ghost riddle about the bologna/baloney sandwich is:
 
Q: What does a ghost eat for lunch?
A: A BOO-logna (BOO-loney) sandwich.
 
The riddle has been cited in print since at least 1974.
 
“What do ghosts eat for breakfast?”/“Dreaded wheat,” “What do ghosts eat for breakfast?”/“Ghost Toasties,” “What do ghosts eat for breakfast?”/“Scream of Wheat,” “What do ghosts eat for lunch?”/“Spookghetti,” “What do ghosts eat for dinner?”/“Ghoulash” and “What do ghosts eat for dessert?”/“I scream (ice scream)” are related Halloween riddles.
       
 
12 March 1974, The Evening News (Sault Sainte Marie, MI), “Mini Jokes,” The Mini Page, pg. 4, col. 1:
Q. What do ghosts eat at picnics?
A. Boo-loney sandwiches.
from Brian Patrick, Stalwart    
 
Google Books
Biggest Riddle Book in the World
By Joseph Rosenbloom
Illustrated by Joyce Behr
New York, NY: Sterling Publishing Company, Inc.
1976
Pg. 65:
What do ghosts eat for lunch?
Boo-loney (bologna) sandwiches.
       
29 October 1980, Akron (OH) Beacon Journal, “The Count’s Creepy Crack-ups,” pg. C2, col. 4:
What do ghosts eat for lunch?
Boo-loney sandwiches.
 
28 October 1984, Newsday (Long Island, NY), “SMiles,” Kidsday, pg. N1, col. 3:
What do ghosts eat for lunch?
Boo-loney sandwiches.
—Cindy Lerner, Plainiew
 
Google Groups: rec.humor
What No Halloween Humor?
Carol Agans
10/30/95
Reminds me of the jokes my daughter came home from school with:
 
Q:  What does a ghost eat for lunch?
A:  A BOO-logna sandwich.
 
23 October 1998, Los Angeles (CA) Times, “Laugh Lines; Pint-Sized Punch Lines,” pg. 2:
What is a ghost’s favorite lunch? A boo-loney sandwich. (Sherry French, 5, Westminster, Richard Pre-School)
 
Google Groups: alt.halloween.boo
Halloween Jokes
stirling
11/8/99
(...)
Q: What does a ghost eat for lunch?
A: A BOO-logna sandwich.
 
Google Books
Dr. Speedy’s Jokes and Riddles
By Speedy Gonzalez
San Jose, CA: Writers Club Press
2000
Pg. 89:
Q: What do ghosts eat for lunch?
A: Halloweenies, Frankenfurters, BOO—loney sand-WITCHES and Ladyfingers for dessert.
 
Google Groups: alt.humor.puns
Halloween Puns of the Weak 10/19/01
Stan Kegel
10/19/01
(...)
What does a ghost eat for lunch?
A Boo-logna sandwich. (Jeff P. Symonds)
 
Google Books
Extreme Monsters Joke Book
By Nikki Bataille Lange
Illustrated by Tim Stuby
Columbus, OH: Brighter Minds Children’s Publishing
2005
Pg. 12:
What does a ghost eat for lunch?
A Boo-logna sandwich!
 
Twitter
100.7 KFM-BFM
‏@kfmbfm
Jack says: What does a ghost eat for lunch?.........Boo-logna!
5:39 PM - 27 Oct 2008
 
Google Books
The Ghost Zone:
Jokes, Riddles, Tongue Twisters & “Daffynitions”
By Gary Chmielewski
Illustrated by Jim Caputo
Chicago, IL: NorwoodHouse Press
2009
Pg. 10:
What does a ghost eat for lunch?
A Boo-logna sandwich!
 
Twitter
Ray Ghoul Rach
‏@rmthack
@choadmalma what does a ghost each for lunch? A Boo-logna sandwhich
2:38 PM - 25 Sep 2009
 
Google Books
Jokes about Monsters
By Judy A. Winter
Mankato, MN: Capstone Press
2011
Pg. ?:
What does a ghost eatforlunch?
A BOO-logna sandwich.
 
Google Books
Insults Anywhere Kids Presents
Joke Book Of The Living Dead
By Franklin Yantz
Published by Insults Anywhere at Smashwords
2011
Pg. ?:
What did the baby ghost eat for dinner?
A boo-loney sandwich!
   
8 November 2015, St. Louis (MO) Post-Dispatch, “Weatherbird’s Top Tweets,” pg. B2, col. 2:
“What does a ghost eat for lunch? A BOO-logna sandwich #STLHalloween #STLtradition” Shuree Sockel, @shuree_sockel