in a similar vain.
some years ago, i got a can of diet pepsi out of a vending machine ..
.. it was empty, although the ring-pull was intact.
i sent it to britvic with a note, telling them that i was not complaining - just letting them know about it (and would they please send it back to m, as i'd keep it for curiosity value)
they not only sent it back - but gave me vouchers to the value of half a dozen more cans, to be redeemed at my local shops.
superb customer service.