A small 50ml pill container.
This cache is part of the Blockbuster A to Z series.
An old 80's gameshow in which contestants had to pick letters and answer questions relating to that letter to get across the board and win.
If we were doing a modern day geocache version of this I would imagine it would go:
AorakiSheep: "I'll have a U please Natalie247."
Natalie247: "Using ROT13 what letter would you need to decrypt to get U?"
AorakiSheep: "It's ....."
Natalie247: "Correct - you might want to store that away for later to see where i go with it."