A "to go" cup that bars in New Orleans and the surrounding areas will pour your remaining alcoholic beverage into so you can take it with you on the drive home.
Due to the lenient attitude towards open containers in this area and the fact that it seems to have always been this way, most people who have grown up here have a hard time adjusting to the fact that a) bars in other cities close at 2 am and b) that they can't take their drinks with them.
And, boy is it fun! :) (See Drive Thru Daiquiri Bar)