Q:
Food Fight mechanics?
A:
Generally people do that to trick clueless players into custom brawl and get easy champion. Mad King food table and pirate cannon are both like that. Since only those who has transformation tonic could go in and out of custom brawl, people would put those things down and wait for others to come and play with them. Once a player touches it, he or she enters custom brawl. A player without a tonic cannot leave the brawl and cannot fight back, so he or she can only be slaughtered by the player who put it down. Your only option here is to waypoint out of there.
Generally you hit F at the table when other brawlers are near. Maybe you have to hit it first? If you see a cloud of BAM POW around you, you did it right.