Champerz is a slang word for the alcoholic drink Champagne which (as the name suggests) is from a region of France called Champagne! It is an expensive drink which ranges in price(from expensive to ridiculous!)depending on quality.
The word champerz is used in the song 'Typical Me' by the East London rapper, from N.A.S.T.Y crew, Kano. Which is a song from his album 'Home Sweet Home'.
From 'Typical Me'-"who is Kano getting in the madness,
me I'm in the pool sippin' on Champerz,"