If you have those plastic dust caps over your crank retaining nuts, a ring pull from a drinks can makes an ideal lightweight screw driver. Fits perfectly.
Mike, would it work on your ‘chrome look’ dust caps 
I’ll bring a can of coke next time we go for a ride, it might not leek as much as that water bag I bought 
Gary
Aha, the complete opposite of the Undersea World of Jaques Cousteau. This strange creature breathing water from a pressurised container strapped to his back.
With hindsight, was Perrier the practical choice for your Camelbak, however chic it may seem? 