The obligation to recite Kiddush on Shabbat morning takes effect only after the recitation of Shacharit. Therefore, before one prays on Shabbat morning, he is permitted to drink tea, coffee and water – those beverages that are allowed to be drunk before the morning prayers. Since the Kiddush obligation descends upon a person only after Shacharit, the prohibition against eating or drinking before Kiddush does not apply before he prays; hence, he is allowed to drink whatever is permissible to be drunk before one prays in the morning generally.
The question arises as to whether or not this Halacha applies to women, as well. According to the Ben Ish Chai (Rabbi Yosef Chaim of Baghdad, 1833-1909), women become obligated to recite Kiddush immediately when they awaken Shabbat morning, and therefore they may not eat or drink anything until they recite Kiddush. Others, however, including the Kaf Ha'chayim (Rabbi Chayim Palachi, rabbi of Izmir, Turkey, 19th century) and Chacham Bentzion Abba Shaul (Israel, 1924-1998), distinguish between women who normally pray Shacharit in the morning, and those who do not. If a woman normally prays Shacharit, then here status is no different from that of a man with regard to this Halacha, and her obligation to recite Kiddush does not take effect until after she prays Shacharit. But if a woman does not normally recite Shacharit, and she recites only the morning blessings and the like, then her Kiddush obligation takes effect immediately when she arises in the morning, and therefore she may not eat or drink anything until she first recites Kiddush. In such a case, when a woman must recite Kiddush in the morning, if she finds it difficult to recite the entire text of Kiddush she may recite from "Ve'shamru," or even from "Al Ken" or just the Beracha itself.
Summary: On Shabbat morning, a man may drink water, tea or coffee before the morning prayers, since the Kiddush obligation has yet to take effect. This applies as well to women who are generally accustomed to reciting Shacharit every morning. Women who normally do not recite Shacharit, however, must recite Kiddush before they eat or drink anything on Shabbat morning, and in such a case they need not recite the entire text of Kiddush.