Trapped in the building with building non-functional is almost a no-win. If you are there for longer than 3 day's (bodys "stay still" ability without water) you probably won't make it. During those 3 days you need signaling more than water. Water is bulky, heavy and noticeable to lug around any usable quantity to meetings with the suits.

That said, I always carry my coffee mug - stainless 16 oz stainless double-walled starbuck travel mug - everywhere because of an ongoing caffiene addiction and it is always acceptable in the meetings. For the healthier crowd 1 liter Evian or similar water bottles seem well accepted. Still bulky and heavy tho....

I think that the building could fall on my coffee mug and not shatter, dent or puncture it.