A water bottle with an (optional) hidden secret. I especially like to use it with lemon slices, though you can use anything.

Great for putting my ice/lemon etc in easily as well as drinking without blocking it up. However, I don't feel like there's any 'give' - if I were to drop it, unlike a plastic bottle, I fear this might shatter/crack easily - not that I intend to drop it but that would be the end of it. The flip top is also not very strong/secure - it's been fine in my bag so far, but I knocked it over yesterday and the weight of the water was enough to pop the top open which has now made me more wary of carrying it in my bag! One that clips somehow would be better. Still using it, just being more careful now!