Toilet Clogging Mystery

Sheboygan police have a mystery on their hands.  Actually a mystery in one of their public restrooms.  Someone has been plugging a toilet in a woman's restroom by inserting a plastic bottle into the toilet's pipe.  It's happened several times over the last three years.  They've had to hang a unique sign in the restroom

showing that no trash should be put in the toilets.  The security cameras show a man in the area so he may be a suspect but no one knows for sure.  Why would anyone do that?  Source: Fox News