“What do little ghosts drink?”/“Evaporated milk.”

“Evaporated milk” is milk that has water removed. A popular Halloween ghost riddle is:
 
Q: What do little ghosts drink?
A: Evaporated milk.
 
“Ghost toasties” and “evaporated milk” was cited in 1940 as the breakfast of “the little man who wasn’t there.” “What do ghosts drink? Evaporated milk” was printed in many newspapers in 1969.
 
“What do you get from an invisible cow?“/“Evaporated milk” is a related joke. “The cows are giving evaporated milk” (Texas heat joke) is a related saying.
   
     
Wikipedia: Evaporated milk
Evaporated milk, known in some countries as unsweetened condensed milk, is a shelf-stable canned milk product with about 60% of the water removed from fresh milk. It differs from sweetened condensed milk, which contains added sugar. Sweetened condensed milk requires less processing since the added sugar inhibits bacterial growth.
 
The product takes up half the space of its nutritional equivalent in fresh milk. When the liquid product is mixed with a proportionate amount of water, evaporated milk becomes the rough equivalent of fresh milk.
         
4 February 1940, Nashville (TN) Tennessean, “Don’t quote me,” pg 2-C, col. 5:
... have you heard about the one about what man who wasn’t there had for breakfast? ... ghost toasties and evaporated milk ...
 
9 February 1940, Ogden (UT) Standard-Examiner, “Sol’s Sunshine and Shadow, pg. 7-A, col. 1:
What does the little man who wasn’t there have for breakfast? Answer: Ghost toasties and evaporated milk!
 
6 July 1969, Indianapolis (IN) Star, “Riddle Box,” sec. 7, pg. 8, col. 6:
What do ghosts drink?
Evaporated milk.
 
Google Books
February 1974, Boys’ Life, “Think and Grin,” pg. 74, col. 1:
Cindy: What do ghosts drink?
Sandy: I know — evaporated milk! — G. Downs, Camden, Ark.
 
4 January 1975, Shreveport (LA) Times, “Riddle Me This,” kids sec., pg. 3, col. 3:
Q: What do baby ghosts drink?
A: Evaporated milk.
Tim Page, 6th grade
Ringgold, La.
 
40 June 1975, The Times Record (Troy, NY), “Fun Time—The Riddle Box,” pg. 30, col. 7:
What does a ghost drink for breakfast?
Evaporated milk.
 
Google Groups: alt.tasteless.jokes
Happy Halloween
Robert Nykvist
10/29/94
(...)
What do little ghosts drink?
Evaporated milk.
 
Google Groups: rec.humor
HALLOWEEN-
Nancy Carson
10/26/96
What do little ghosts drink?
Evaporated milk.
 
Google Groups: alt.support.depression.manic
Final Jokes (Some Raunchy and Some Political) from James
James D. Milton
11/1/98
“Halloween Q & A”
(...)
Q: What do little ghosts drink?
A: Evaporated milk.
 
Google Groups: alt.humor.puns
Halloween Puns of the Weak 10/19/01
Stan Kegel
10/19/01
(...)
What do little ghosts drink?
Evaporated milk.  (Paul Croft)
 
Google Groups: alt.humor.puns
Puns of the Weak 11/29/02
Stan Kegel
11/29/02
(...)
What do ghosts like to drink?
Evaporated milk (Zack, 10)
 
Google Books
Blonde Walks into a Bar:
The 4,000 Most Hilarious, Gut-Busting Gags, One-Liners and Jokes
By Jonathan Swan
Berkeley, CA: Ulysses Press
2008
Pg. ?:
What do little ghosts drink?
Evaporated milk.
 
Google Books
The Ghost Zone:
Jokes, Riddles, Tongue Twisters & “Daffynitions”
By Gary Chmielewski
Chicago, IL: Norwood House Press
2009
Pg. 10:
What do little ghosts drink?
Evaporated milk!
 
Twitter
Stephen Scarris
‏@scaryjokes
Spook talk #2: What do ghosts eat for breakfast?  Ghost toasties and evaporated milk.
4:06 PM - 17 May 2009
 
Twitter
Daily Groaner
‏@DailyGroaner
Q:What do little ghosts drink? A:Evaporated milk. #halloweenjokes
12:40 PM - 27 Oct 2009
 
Google Books
Horrid Henry’s Joke Book
By Francesca Simon
Naperville, IL: Sourcebooks Jabberwocky
2010
Pg. 9:
What do little ghosts drink?
Evaporated milk.
 
Google Books
Halloween Ghost Jokes For Kids 3
By Peter Crumpton
PeteyRF Creative
2015
Pg. ?:
What do little ghosts drink?
Evaporated milk.