Have you ever tried sucking in from a helium balloon? From my understanding the density of the helium is lower than the air we breathe which then makes the sound travel faster and changes the way the vocal tract vibrates changing your voice like that... Idk if helium beer is an actual thing though or these guys just hoaxed it from what im reading now... but either way helium does make your voice like that and the video is actually hilarious either way!