warm piss 

A bad/cheap alcoholic beverage, generally with a low alcohol content

Did you try that disgusting microbrew i told you about?
Yeah man, it’s warm piss. Whoever made it must’ve just left some wheat grain in dishwater for a week.

warm piss by Atreides, Leto March 11, 2020

Pissing in One's warm spot 

Taking something that someone finds joy in and describing it as joyless and inferior. Taken from lake swimming where you can find occasional warm spots; telling someone about it may lead them to come over to share the warm spot, only to take a piss.

"I am in love with this video. 1000 musicians got together to play a song to get foo fighters to come to their tiny Italian village."
"I guess. I prefer the actual Foo Fighters version though if I'm going to listen to something."
"Stop pissing in my warm spot."
First person "Pissing in one's warm spot."

Pissing in One's warm spot by GreetingsADM September 4, 2015