Here is a portable Bluetooth speaker that relies on an empty bottle to give you a richer, louder listening experience. The SODAPOP runs on a battery that lasts up to 30 hours. The external bass bottle increases the volume of the speaker by 10 decibels.
The bottle doubles as a protective carrying case for the speaker. The SODAPOP speaker is IPX5 waterproof. You simply have to connect a regular soda bottle to double the bass.[where to get it]