Steve shakes his head, not for Tony's sake or anything. When he's done, Steve takes the bottle and fills it up the rest of the way, capping it for Tony so he can drink from it later.

As far as Steve is concerned, in this kind of environment and in their line of work, it's not about dues. If they take care of each other and keep an eye on each other, that will be the only way they can manage through.

He taps Tony on the wrist, because he's got somewhere to take him.