It is short for beverage.
The word is usually used to refer to an alcoholic beverage.
The word has been popularised because of its heavy usage by a character named Thuso ‘Cobra’ Mokoena on a popular TV series called The River.
Lmao Sunscreen will be packed, metsi le di ice re sorted. Kere le Bev ereng mo baneng 😂😍 https://t.co/082YhuDi5Y
— Letso (@MatsieSekoaila_) December 13, 2018