It is not magic or engineer’s skills… You can buy this “thing” from Eric Goldfarb.
The Firefly, Invented by Eric Goldfarb is a unique design which turns your bottle into a lantern. The Firefly’s unique design allows it to be used right side up, upside down, or hanging from the nearest handy branch.
Firefly contains an integrated LED light which spreads a warm glow throughout the bottle. It has variable light levels so you can have a nightlight for stormy nights, or a reading light for enjoying your latest read; the control is at your finger tip! The electronics are in a separate sealed compartment, so there’s no risk of water or juice gumming up the works!