“I do my best thinking when I’m drinking”

” I do my best thinking when I’m drinking” is a T-shirt slogan. The saying has been cited in print since at least 2006.
 
 
Zazzle.com
I Do My Best Thinking When I’m Drinking Shirt
               
Lunatic Radio
Chris From Somewhere
Posted: Sun Jun 18, 2006 12:30 am
Jon has said I do my best thinking when I’m drinking, and even though this certainly isn’t the most original idea:
 
Third Generation F-Body Message Boards   
tocoso
03-19-2007, 09:29 PM
(...)
Just to let you all know I do my best thinking when I’m drinking.
 
FanStory
Posted:  April 8, 2008
Just an Average Day
Early Morning to Late Evening by Annmuma
(...)
Before long, I’m feeling sweet and mellow
I notice my honey’s quite the fellow.
Pull down the covers, fluff up the pillow:
I do my best thinking when I’m drinking!

Google Books
Fantasies and Fare
By Wally Ford
Xlibris Corp
2010
Pg. 56:
Today I wanted to get started early.
I walked to my favorite fishing hole,
On the river to do some thinking.
There was bourbon in the bag I’d brought with me,
Cause I do my best thinking when I’m drinking.