Play video content EXCLUSIVE Facebook Russell Swindells

An ICP fan got punched in the face by Shaggy 2 Dope after he broke the cardinal Juggalo rule: don't waste a Juggalo's soda.

A rep for ICP tells us the fight started when a fan wouldn't stop chucking plastic, unopened bottles of Faygo onstage towards the band at their show a couple of weeks back.

For non-Juggalos, Faygo is a cheap, sugary, carbonated soda that's culturally important in the Juggalo world. ICP made Faygo famous by giving fans "Faygo showers" and spraying them with their fav soda.

The rep says Shaggy felt provoked and was only trying to protect himself and his partner in rhyme, Violent J, from physical injury ... so he jumped into the crowd and laid into the Faygo-thrower.

We're told security broke it up and escorted the fan out of the venue.