“Hey, bartender!” is an iconic phrase, popularized as the title of a 1954 song by Floyd Dixon and repopularized when that song made the album Briefcase Full of Blues (1978), by the Blues Brothers. “Hey, bartender” has been cited in print since at least 1879. Print citations of the phrase were few during the U.S. prohibition (1920-1933), and then many citations appeared from the mid-1930s. “Hey Bartender” was also the title of a 1946 song.

 
Wikipedia: Hey, Bartender
“Hey Bartender” is the title of a song written by Floyd Dixon in 1954, covered and recorded live by the Blues Brothers in 1978 and recorded American country music artist Johnny Lee. It was released in June 1983 as the first single from his album Hey Bartender. The song reached #2 on the Billboard Hot Country Singles chart and #1 on the RPM Country Tracks chart in Canada.
       
24 April 1879, Jeffersonville (IN) National Democrat, pg. 7, col. 4:   
’‘Hey, bartender, you vas guess how many of dem cabbages in das bag, I gif you der whole five.”
 
19 February 1908, The Evening Times (Grand Forks, ND),  “Fight Masters Outside Ring,” pg. 3, col. 4:
“hey, bartender, open a bottle of wine!”
 
19 August 1935, Evening World-Herald (Omaha, NE), “Joe Palooka” comic strip, pg. 15, col. 1:
“HEY BARTENDER GET MOVIN’..YOU’RE WAITING ON GENTLEMEN!”
 
26 June 1936, Canton (OH) Repository, “Convention Nights Wildest Since 1776,” pg. 21, col. 2:
Hey, bartender, we’re delegates to the Democratic national convention. Set up another round!
 
8 November 1936, The Capitol Plaindealer (Topeka, KS), “World of Sports” by Frank Marshall Davis, pg. 8, col. 8:
“Hey, bartender! Go see what the boys in the back room will have!”
 
Google Books
6 April 1946, The Billboard, pg. 34, col. 2:
HEY! BARTENDER Curt Barrett and the Trailsmen King
 
OCLC WorldCat record
Up this hill and down
Author: Osborne Brothers.
Publisher: New York : Decca, [1966]
Edition/Format:   Music LP : Bluegrass music : English
Contents: Hey, hey, bartender
 
OCLC WorldCat record
Briefcase full of blues
Author: Blues Brothers.
Publisher: Japan : Atlantic, 1978.
Edition/Format:   Music LP : Blues : Multiple forms : English
Contents:  Hey bartender.
 
OCLC WorldCat record
Hey, bartender : one more round.
Author: Jarrett H Nash
Publisher: [S.l.] : Authorhouse, 2009.
Edition/Format:   Book : English