https://www.wired.com/review/sodapop-bluetooth-speaker/
KEY EXCERPTS:
Sodapop is a one-of-a-kind super compact Bluetooth speaker that can be screwed onto a standard soda bottle .. ..transformed into a bass chamber that, .. boost the speaker’s bass output by up to 10 decibels. .. this configuration will double the perceived volume in the mid-bass range. .. .. the acoustically tuned plastic bottle does indeed boost the lower frequencies, and makes the speaker sound significantly better..... You can really hear the difference in the mix and balance, and the contrast between the sound with the bottle on and off is impressive. ... Sodapop does work, and it looks pretty .. but there are better sounding, more versatile, and smaller speakers available for less. $89