“I always feel sorry for people who don’t drink, because when they wake up in the morning, that’s as good as they’re gonna feel all day” was said by the actor Jack Lemmon in the movie Under the Yum Yum Tree (1963). Both the movie and the 1960-61 play were written by Lawrence Roman (1921-2008).
 
The line has frequently been credited (incorrectly) to Frank Sinatra, Dean Martin, Sammy Davis, Jr. and W. C. Fields.
 
   
Wikipedia: Under the Yum Yum Tree
Under the Yum Yum Tree is a 1963 comedy movie that stars Jack Lemmon, Carol Lynley, Dean Jones, and Edie Adams, with supporting roles by Imogene Coca and Paul Lynde.
 
This sex comedy was one of the successful small comic movies that Lemmon despised making (despite him gaining a Golden Globe nomination). The film was based on a Broadway play that first ran in 1960–61.
 
The Internet Movie Database
Memorable quotes for
Under the Yum Yum Tree (1963)
Hogan: I always feel sorry for people who don’t drink, because when they wake up in the morning, that’s as good as they’re gonna feel all day.
 
12 September 1963, Wisconsin State Journal (Madison, WI), “It Happened Last Night” by Earl Wilson, sec. 1, pg. 7, col. 2:
It’s Jack Lemmon’s line in “Under the Yum Yum Tree”: “I feel sorry for people who don’t drink. When they get up in the morning, that’s the best they’re gonna feel all day.”
     
18 March 1964, State-Times (Baton Rouge, LA), “TV Closeups” by Alex Freeman (Bell-McClure Syndicate), pg. 4-D, col. 3:
Here’s a Molly Beeism: “I feel sorry for people who don’t drink, ‘cause, when they wake up in the morning, that s as good as they re going to feel all day.”
 
7 October 1965, Los Angeles (CA) Times, “Roz Russell Helps Dodgers Celebrate ,” pg. D17:
“I remember what a Mexican bartender told me once: ‘I feel sorry for people who don’t drink. When they wake up in the morning that s the best they ll feel all day.’”
 
Google News Archive
15 February 1979, The Free Lance-Star (Fredericksburg, VA) , “Who Said It?,” pg. 4, col. 6:
I feel sorry for people who don’t drink, because when they get up in the morning, that’s as good as they’ll feel all day.— W. C. Fields.
   
Google Books
Crazy Heart
By Thomas Cobb
New York, NY: Harper & Row
1987
Pg. 181:
“I feel sorry for people who don’t drink. They wake up knowing that’s as good as they are going to feel all day.”
“Jack Lemmon. The Apartment. Funny line as long as you don’t believe it.”
 
Google Books
The Quotable Drunkard:
Words of Wit, Wisdom, and Philosophy From the Bottom of the Glass
By Steven Kates
Avon, MA: Adams Media
2011
Pg. 99:
” always feel sorry for people who don’t drink, because when they wake up in the morning, that’s as good as they’re gonna feel all day.”
—HOGAN, UNDER THE YUM YUM TREE
This quote has been variously attributed to Frank Sinatra, Dean Martin, Sammy Davis Jr., and Anonymous.
 
Google Books
All Kinds of Humor: Jokes, Quips, and Fun Stuff for Many Occasions—Book 1
By Frank Verano
Xlibris Corporation (Xlibris.com)
2012
Pg. 198:
I feel sorry for people who don’t drink. When they wake up in the morning, that’s as good as they’re going to feel all day.”—Frank Sinatra