There's a trick campers use, where they shine a flashlight down into a water bottle to create a lantern. Well, Italian cycling goods manufacturer Elite uses that same principle in its new Candea bottle – LEDs in the bottom illuminate the bottle above, making night-time cyclists a bit more visible.
The Candea's IP66-waterproof lights are powered by two CR2032 coin-cell batteries, which should be good for about 60 hours of run time before needing to be replaced. It's possible to set those lights to one of three modes – maximum brightness, energy-saving (50 percent brightness) or flashing.
Because the 650-ml BPA-free polyethylene bottle itself is translucent, the "lantern" effect should probably work even when it's not holding any water. That said, it looks like Elite expects users to fill the bottle with water before making night-time commutes, without the intention of drinking it – the bottle's use as an actual source of drinking water would presumably take place during daylight hours.
The Candea is available now, for US$30. For about the same price you can also get Topeak's similar-but-different iGlowCageB, which uses an RGB LED in the bottle cage to illuminate the bottle in different colors.