By Lauren Haughey Bananas, cherries and peaches are among countlessfoods that may have a saucy meaning when used in the right setting – but have you ever wondered about pineapples? Believe it or not, these spiky fruits mean something completely wild when turned upside down and are often spotted on cruises, according to experts. They usually crop up anywhere from bedroom doors, to Hawaiian shirts, as likeminded holidayers seek to communicate through this unspoken language. “On a cruise ship, the secret symbol of an upside-down pineapple is regularly used as a code for swinging or ‘wife-swapping…