1913 Water Doing

So I was thirsty recently. Perhaps because I was listening to that old song by the Australian group Midnight Oil. The "Time Has Come, Beds are Burning" one where they sing about the western desert being 45 degrees.
As the rest of the song is about hot stuff, I never really got that. 45 degrees is pretty chilly. Then I finally realized. They're Australians. They're talking 45 degrees Celsius. That’s 113 around here.
That's why I got thirsty. So I grabbed a bottle of water and a couple of things struck me. One, the water had a pull date on it. Really? What have they added to the water which will make it go bad if left to sit for too long? I may want a case or two of this stuff in my apocalypse survival shelter. Who wants to survive with stale water?
Ick.
The other thing I noticed was how I drank the water. I unscrewed the cap. Then I took a drink. Then I did a funny thing; I re-screwed the cap back on.
As if I was actually trying to preserve its freshness. Like it was a carbonated drink or something, or a wine whose trip to vinegar-hood I didn't want to hasten.
Kind of funny really, because if I had poured a glass of water from the bottle, or from the water cooler in the office kitchen, or the dispenser in my refrigerator door whose tubes I haven't cleaned in 15 years, I wouldn't have thought twice about leaving it exposed. My glasses have no lids.
But with my little bottle, I re-screwed on the cap. Maybe my memory was warning me about evaporation.
From all that time I toted my canteen in the 45 degree desert.
America, ya gotta love it.