Rum

Rum is a strong alcoholic drink that has been historically linked with pirates in particular and sailors in general. It is distilled from sugar cane and thus was abundant in the heavily pirated Caribbean.

Rum was also the official drink of the British Navy; this was originally brandy, but was later changed to rum simply because it was cheaper.

One Piece
In One Piece, rum and other alcoholic beverages such as sake are prevalent throughout the series. One of the more prominent cases is the song Bink's Sake which is a typical pirate song about delivering alcohol.