Your body needs fluids before, during and after skiing, even if you don't feel thirsty. In fact, it's possible to be close to dehydration without feeling the urge to drink. Regardless of whether you sweat a little or a lot when exercising, you should be conscious of the fact that you're losing fluid. You need to be proactive about drinking throughout the day. Other fluids, including caffeinated and alcoholic beverages have undesirable effects, including water loss, decreased body temperature and slowing of reflexes.
Water mixed with a powdered sports drink is a good alternative to just plain water.
Drink plenty of water before you start out for the day, regardless of the weather conditions. Bring along a water bottle in a waist pack to keep yourself hydrated while out on the slopes. Try to drink a bottle in the morning and one in the afternoon. You may also want to investigate a back-mounted hydration system for your ski outings. Drink small amounts of water in frequent intervals rather than large gulps.