Cold water is fine for sipping in the restaurant. However, when you are thirsty and are going to pound down 8 oz to a quart in less than a minute I will say stay away from the cold stuff.
In my late 20's I discouvered this. I'd go out and sweat for an hour get a few minutes break before starting again. In that time I would gozzle water from the fountain. It didn't take more than a few episodes of cramps and charging to the can to make the connection. I started carrying a water bottle after that discouvery. Now, I prefer to drink room temperture or only cool water. I usually down 10 oz in a single drink and then start the second 10 oz.
In fact, if I down 10 oz of cold water (tap cold not ice cold). I will breakout in a sweat in about a minute. The message is the body's thermal regulation system is quick and drastic. Also if the brain gets mixed signals, that triggers survival reactions. It figures it's getting mixed signals because something is wrong... like you've eaten someting bad so start the evacuating.
That's a little more than just loosing the energy needed to heat it. Althought I'm sure that's important too.
Sending love,
Iam2 
