Ryan Robinson, 25, shared the close encounter with the wild animal in a video clip on Facebook.
According to the Manchester Evening News, Ryan was filling up his car with oil when he placed the warm brew on the side of the road.
In the clip, he is heard shouting at the fox: “Oi – get away from my brew.”
However, the nocturnal creature was having none of it and cocked its leg and urinated in the cup.
The fuming airport worker then moaned at the fox: “You little s**t.”
Before adding: “Wow, a fox has p***ed in my brew.”
The video has now gone viral and clocked up over 33,000 views.
Ryan commented: “It’s taken me by surprise the amount of interest in it.
“It’s something you don’t see every day.”