I've never dropped it but had the experience of two Aluminium bottles jumping off the bike as I descended a bumpy, and steep hill at 40mph or so on my Dahon Speed-Pro folder, 20" wheels 120psi tyres and big bumps are not a good mix. As I hit one very big bump I watched the one attached to the handlebars lift and slow, I decided to let it go rather than risk trying to catch the damn thing so it bounced off my leg and disappeared from view. As I braked to a stop, the handlebar mounted one went sliding past me, then as I put a foot down something to hit my foot, hard! I'd lost one mounted behind the seat on the same bump, and that one had got me. I still have the two very battered aluminium bottles. I can speak from experience that 500+ml of water in a metal bottle, still going at a fair clip really stings.