when a man does not wash his balls for an excess amount of time collecting the vinegar smell of the disgusting ball sweat for maybe a week or two, knowing he will be receiving oral pleasure from his female friend, and he sticks the nasty balls in the womans mouth making her clean them.
guy 1: whatd you do to my sister lastnight?!
guy 2: i gave her a vinegar surprise
guy 1: sick! thats my sister!