The next-best thing to ice.
BCB International has recently developed a heat-defying water
cooling system which attaches to any hydration system to provide a
cooled drink, rather than a mouthful of warm water which has been found
to discourage soldiers from regular drinking. Affectionately named the
'Chilly', the portable cooling system weighs a sleight 400
grams, and cools the water as it travels through a succession of cooling
fins, each of which contains a wick that transfers a small amount of
water to the outer covering, where it evaporates - taking heat with it.
Using this heat transfer, the unit can reduce the temperature of the
drinking water by up to 25[degrees] C. The Chilly works without
batteries and incorporates silver as an antimicrobial element. Tests
from soldiers in Afghanistan have confirmed its ability to keep soldiers
hydrated and feel cool for longer periods. Cooler water means the
soldier enjoys drinking. BCB International mentions the system can
simply 'click' into most military hydration system (portable
water reservoir with a built-in flexible drinking tube).