Jae Han Gi - Hapkido Master - My Dojang had him in for a few seminars and he was very specific about not drinking cold water. If he did have to drink chilled water he would use his tongue to cover his molars while the water went down.
His reasoning was that he wanted to be in complete control of any adrenal bursts from his body. The cold water rushing over the molars would cause a little shock pumping adrenaline.