These were posted elsewhere on forum. Just to refresh our memories! The first one a televised program of the slingshot event, an Asian winner. The shooting starts at around 3 min 20 sec into the video. Cans appear to be unopened/sealed with whatever beverage contents.
This is Brunetti Marco and his slingshot attempt at record. Cans are also full & sealed with beverage contents.
Maybe Guinness just assumed or that it was understood that cans are full/sealed and therefore not in the guidelines?? If so they should make clearer and amend it or something.
May the FORCE be with you MJ ... the good force ... maybe you want to change your avatar to Luke Skywalker