My childhood in the 1970s was marked by high gas prices and inflation. In particular, I remember coffee prices being very high and my parents often reusing the coffee grounds. To entice customers to eat out, restaurants would often advertise a "bottomless cup of coffee". In my naivity I used to believe that a "bottomless cup of coffee" meant you could drink as much coffee as you wanted before it ran out of the 'bottomless' cup.
A childhood belief about drinks

others believed things like this
- I always refused to eat coffeecake because I thought it was made with coffee grounds. Anon
- I used to think it was illegal for children to drink coffee— C.W.
- I always thought there was a drinking age for coffee, because it was an adult drink like beer and wine.Anon
- I used to believe that the term "being mugged" meant someone beat someone else with a coffee mug.— Matt Thiel
- I used to believe that coffee was tea with milk in it.Anon
- I thought you could get toffee from mixing tea and coffee.Anon