...and I can imagine that after you fil your water bottle, some airhead security person will tell you that you cannot bring it through security!!!!!
This is a problem at AMS, because there is at most gates (inside security) nowhere at all where a bottle of water can be purchased at any price, and even at the gates with vending machines they are often not stocked. The sealed bags are used for duty free but I don't believe they will put water in them even if you ask.