When I was a kid I remember hearing the recommendation to drink 8 glasses of water a day. For some reason I didn't get the "a day" part, so i thought i had to drink it all at once. That seemed impossible to me so I gave it a try one day, chugging water as quickly as I could, and got sick by about the second or third glass.
A childhood belief about drinks

others believed things like this
- I thought tonic water was toxic water and wondered why would anyone drink it if it is toxic?— Dr.Badguy
- When I was young I refused to drink well water because I thought it came out of whales.— itodd
- My mum used to tell me that you couldn't drink water out of the tap from the bathroom as it was poisonous.Anon
- I used to think that if I ate a fruit seed it would grow in my stomach if I drink water after thatAnon
- if you drink water from unsafe places, frogs will grow in your stomach...— Olivier
- I used to think that if you mixed a diet drink with a regular drink, it would explode. Anon