A stainless steal flask, with an elegant mustache displayed on the front, towards the mouth piece of the flask, that while taking a swig gives people the illusion you have a mustache.
Typically filled with strong whiskeys or vodkas and is generally used quite frequently throughout a given night until a person is unexpectedly shit face drunk. Usually takes fellow peers and spectators by surprise, seeing you are probably doing things you typically would never do.
Most commonly leads to mustache fights, mustache man, mustache humping, Mustache rag, Mustache water
And lastly in all seriousness, Mustachatory Rape.
Bill: Woah, did you see your mom over there making out with your sisters boyfriend???
Andrew: Holy shit! She must have been hitting the mustache flask hard!
Bill: That's what i figured. We should snatch that away for ourselves and hope for a mustache fight!
Andrew: : /