A popular joke is told at the beginning of baseball season:
 
Q: Why did they stop selling beer at the baseball park?
A: Because the Mets/Yankees lost the opener.
 
The joke has been cited in print since at least 1952.
 
   
3 June 1952, Waukesha (WI) Daily Freeman, “Up and Down Broadway in Waukesha” by Tom and Gene, pg. 6, col. 3:
Spare Us Just This One Time
When we told a beer-drinking friend of ours recently that the new Brewer ball park policy is to prohibit the sale of beer, he asked the obvious question: “Why?”
 
We were then forced into giving the obvious answer: “Because they lost the opener.”
 
Google News Archive
21 April 1954, Milwaukee (WI) Sentinel, “Look What a Three-Cent Stamp Buys These Days!” by Buck Herzog, pt. 1, pg. 8, col. 1:
I’m working because I was told there was not going to be any beer sold at any of the Braves’ games. Why? Because the Braves lost the opener.
     
14 July 1957, The Sunday Star (Washington, DC), “The Baseball Beat” by Burton Hawkins, pg. C-3, col. 7:
Rocky Bridges says the Senators should air condition Griffith Stadium by putting a fan in every seat…And if that isn’t bad enough he adds that the reason they didn’t sell beer there for so many years was that on too many occasions they lost the opener.
 
Google Books
Medical Times
Volume 86, Part 2
1958
Pg. ?:
One day, a little patient entered the office and said to me, “Doc, they won’t be able to sell beer at the park any more.”
 
“Why?” I asked him, really worried!
 
“Because the Cards lost the opener!”
 
Google News Archive
21 July 1970, Pittsburgh (PA) Press, “The Night Beat” by Lenny Litman, pg. 9, col. 3:
And in case you just came back, the joke sweeping the town is: “Do you know they are not going to sell any more beer at Three Rivers Stadium because the Pirates lost the opener.”
 
Google News Archive
4 April 1989, Daily News (Bowling Green, KY),  “Opening day a happening for Cincinnati Red’s fans” (AP), pg. 1-B, col. 1:
Now that the Reds have won seven straight opening day games, the old joke has died about there being no more beer at the games because “the Reds lost the opener.”
     
ClutchFans (Houston Texans)
Minute Maid park to stop selling beer
rockHEAD
04-07-2004, 03:55 PM
cause they lost the opener….
 
VTXOA Mesage Boards
Outlander
04-09-2005, 01:06 PM
On topic would be unbelievable.
So…
Mr. V, did you hear they’re not selling beer at the Metrodome this year?
No, Mr. X, why is that?
The Twins lost the opener!
 
The Sundry Times
07 Tuesday Apr 2009
No Beer
Posted by Gary Zimmerli
I see they won’t be selling beer at the Metrodome this summer.
The Twins lost the opener.
(Hardy-har-har-har!)
 
Twitter
Staci Sharik
‏@staci_amanda21
“Why did they stop selling beer at the baseball park?”
“Because they lost the opener.”
-my grandpa
11:13 AM - 11 Apr 2015
 
TheNorthwestern.com 
David Hayford: Big week for Wisconsin sports, politics
David Hayford 12:12 p.m. CDT April 13, 2015
Big week. In chronological order, Brewers’ opener, NCAA final, Election Day.
 
I won’t say much about the Brewers first game. Except to repeat the old joke: “they won’t be selling beer at Miller Park this year.” “Really?” “Yep, the Brewers lost the opener.”
 
Twitter
Zach Hudson
‏@zahudson95
Dr Smith: If the Twins lose today, Target Field can’t sell beer for the rest of the year.
Class: Why?
Smith: They will have lost the opener.
Arden Hills, MN
3:02 PM - 13 Apr 2015