At uni, I once decided I could eat ‘corn pops’ (retro cereal) whole by just swallowing them. The first was ok, but must have totally dried my throat out as the second slid down & stopped. Once I started going blue, my girlfriend at the time stopped laughing & slapped me really hard on the back & it sailed across the room.
Same girlfriend had a younger brother who stuffed a hearing aid battery down his ear as he thought it would make him hear better.
And the best one was a bloke in my brothers year at school who used to play in the road with us. The buckle of his Casio watch had snapped so he was riding round the street with the strap held between his teeth. He hit a small pothole & somehow managed to swallow the watch! He made it into the Wembley Observer newspaper & a week later when the watch came out it was still working!