http://revach.net/article.php?id=2864

Section: Halacha   Category: Succos
The Chofetz Chaim & Rav Shlomo Zalman Auerbach: Can You Drink Water Outside A Succah?
The gemara says that the Mitzva of Yeshivas Succah is to eat and drink in the succah.  Since we know that only eating a Kevius requires a succah and not drinking (even wine according to most poskim), why does the gemara say it is a mitzva to drink in the succah. 

The Chofetz Chaim in Shaar HaTziyon (639:29) suggests that drinking during a meal might require a succah since drinking is part of the kevius se'uda.  Therefore he says that it may be a problem to drink water outside the succah during the meal.

Rav Shlomo Zalman Auerbach says that while drinking outside the house is normal all year round and therefore permissible outside a succah, if however you are near your succah it seems that you might be obligated to go inside to drink.  The reason, he says, is that if some if someone is standing near their home they would go inside for a drink.

Important Note: We try to convey the Tshuva to the best of our ability. We admit that our understanding maynot be accurate. Please also understand that this Tshuva may not be the final word on this topic. One should consult a Rav before drawing any conclusions.