Show the bottle to be empty other than some water and that nothing is hidden under the cap
Take a band off your wrist and you place it around the bottle.
With a wave of your hand the band penetrates the bottle and sinks to the bottom
When your spectator(s) are done swearing and just before they threaten to burn you for the crime of witchcraft, hand them the bottle for examination
Water Logged is a seemingly impromptu effect that is very easy to do and leaves your spectator with an impossible souvenir