I knew about this puzzle at Puzzle World, from where it was removed due to problems with the original name (it was made with a bottle of a well-known drink).

The bottle contains a chain with a brass padlock on one end and is joined to the cap on the other. If it weren't for the chain link straddling the shackle of the padlock, the chain and the padlock would slip right throught the neck. The keys to the padlock are clipped to the chain and easily removed. The objetive is top remove everything in the bottle.

• Solution

I do not write it here because I'm not sure if mine is actually identical to William's. Anyway it's a nice one.