I had a normal water bottle and it was fine after showing my proctor that nothing was written on or taped to it. I did dump most of it on myself accidentally during the 3rd section though, so make sure your lid is on well! LOL
Speaking of the answer keys, sometimes I've accidentally scrolled over the icon that covers the correct answer choices and wish there was a way to completely hide them so we don't do that by mistake. I don't know if it can be done, though.