BYOB changes with age. As a child it simply stands for bring your own bed, used mainly during a sleepover to say, "bring a sleepingbag" as you get older, it means bring your own beer,as beer will not be served.
Johnny(age 5) BYOB, friends, it'll be a great sleepover!
BYOB is an acronym with several similar yet related expansions. The acronym is most often associated with a social gathering (a party) at which the host will not be providing alcoholic beverages; the guests are invited to bring a beverage of their choice for their own consumption.
Common expansions of the acronym include:
Bring Your Own Bottle
Bring Your Own Booze
Bring Your Own Beer
Bring Your Own Beverage