“On a New York City subway you get fined for spitting, but you can throw up for nothing” is a jocular saying that has been printed on many images. “Strange thing about the subways in New York. You spit and they fine you $25, but you can throw up for nothing” was said by a New Yorker and quoted in a Lewis Grizzard (1946-1994) newspaper column in the Atlanta (GA) Constitution on October 18, 1978.
   
“Which reminds me of a sign I saw in a New York subway once. It said: ‘Spitting is a $50 fine.’ And I thought, ‘I guess you can throw up for nothing’” was printed in Grizzard’s column in the Atlanta (GA) Journal-Constitution on July 10, 1992.
   
         
Wikipedia: Lewis Grizzard
Lewis McDonald Grizzard Jr. (October 20, 1946 – March 20, 1994) was an American writer and humorist, known for his Southern demeanor and commentary on the American South. Although he spent his early career as a newspaper sports writer and editor, becoming the sports editor of the Atlanta Journal at age 23, he is much better known for his humorous newspaper columns in the Atlanta Journal-Constitution. He was also a popular stand-up comedian and lecturer.
         
18 October 1978, Atlanta (GA) Constitution, “Ballplayers: TV Shows Your Spitting Image” by Lewis Grizzard, pg. 1-C, col. 1:
It’s like a New York mentioned to me recently.
 
“Strange thing about the subways in New York,” he said. “You spit and they fine you $25, but you can throw up for nothing.”
 
Google Books
The Fourth—and by Far the Most Recent—637 Best Things Anybody Ever Said
By Robert Byrne
New York, NY: Atheneum
1990
Pg. ?:
477
On a New York subway you get fined for spitting, but you can throw up for nothing.
Lewis Grizzard
     
10 July 1992, Atlanta (GA) Journal-Constitution, “Washouts aside, garden grows fine” by Lewis Grizzard, pg. G1, col. 1:
... which reminds me of a sign I saw in a New York subway once.
   
It said: “Spitting is a $50 fine.”
   
And I thought, “I guess you can throw up for nothing.”
   
Google Groups: rec.sport.football.pro
NFL predictions
John R Tedrow
7/19/97
(...)
On a New York subway you get fined for spitting, but you can throw up for nothing.
-Lewis Grizzard
     
Google Books
Dim Wit:
The Funniest, Stupidest Things Ever Said
By Rosemarie Jarski
New York, NY: Random House
2008
Pg. 171:
On a New York subway you get fined for spitting, but you can throw up for nothing.
Lewis Grizzard
 
Twitter
Jon Winokur
@DailyCurmudgeon
On a New York subway you get fined for spitting, but you can throw up for nothing. LEWIS GRIZZARD #quote #quotes
7:02 PM · Jun 11, 2009·Twitter Web Client
 
Twitter
Steve Cirillo
@StevenCirillo
On a New York City subway you get fined for spitting, but a random crazy can throw up without penalty. #hmmm #weirdrulesofNYClife #fb
3:14 PM · Jun 2, 2011 from Manhattan, NY·Twitter Web Client
   
Twitter
Loredana Gasparotto
@Anaderolart
On a New York subway you get fined for spitting, but you can throw up for nothing. – Lewis Grizzard😜😳😳
@creativeendev
#NY #subwaytrack #chinatown #littleItaly
Art Film Art and 7 others
9:38 PM · Dec 8, 2018 from Queens, NY·Twitter for iPhone