When you don't check the serving size while preparing your Swiss Miss Instant Chocolate.
According to Sam O'nella the chocolate tastes like piss. So you unleash a primal roar of sheer fury, the cat shits itself and jumps out the window as you kick the Swiss Miss box across the room.
When you really need to take a piss, in reference to Sam O'nella's Swiss miss video where he called it:
" Swiss Miss, Instant Piss" in regards to the taste of only one packet.