Empty "thermos"type coffee mugs must go too as they are of a greater volume than 100mls.....................
Well according to GLA security anyway, I asked if he wanted my boots too
I've blatantly taken empty water bottles through security before now, the regs are obviously different at GLA. Even the time when I was pre-selected for extra security, the security team didn't object to the empty bottle.
My understanding is that it's the presence of the liquid that's important, not the container, given that it's trivial to go buy a new container once airside.