It name-checks various alcoholic beverages[2] - Wiser's (or alternately Budweiser), Jack Daniel's, Jim Beam, Johnnie Walker (Black and Red Labels), and Old Grand-Dad - in the verses.
[4] George Thorogood wrote I Drink Alone as a dedication to American film and television actor Lee Marvin.
Thorogood then opens his guitar case, and takes out an alcoholic beverage, and glass and starts drinking.
The video then cuts to Thorogood playing the solo on his guitar, after which he goes back to drinking alcohol and singing.
[1] AllMusic critic James Christopher Monger called "I Drink Alone" one of Thorogood's "high points".