There is an obligation to recite Kiddush over a cup of wine on Friday night, and the Shulhan Aruch (Orah Haim 271:6) rules that once Shabbat begins, it is forbidden to eat or drink anything including water before reciting or hearing Kiddush. This means that if a person is in the synagogue after sundown on Friday night, he may not have a sucking candy, or even a drink of tea or water. Since Shabbat has begun, and thus the obligation of Kiddush has taken effect, he may not eat or drink anything before Kiddush. This applies even in the summer months, when many communities have the custom of accepting Shabbat well before sundown. Thus, for example, if a person returns home from the synagogue on Friday night before sunset, and he needs to wait for the other family members to complete their Shabbat preparations, he may not have a snack or drink. Since he already accepted Shabbat, he may not eat or drink anything before Kiddush.
As the Kiddush obligation applies equally to men and women, both men and women are included in this prohibition against eating or drinking before Kiddush.
An important exception to this rule is noted by Hacham Bension Abba Shaul (Israel, 1923-1998), in Or Lesion (2:46), where he writes that this Halacha was instituted only for those who have reached the age of Misva obligation. Minors boys before the age of thirteen, and girls before the age of twelve may be fed if they wish to eat or drink before Kiddush. Although children approaching the age of Misva obligation should be trained to refrain from food and drink before Kiddush, as a general rule parents should not hesitate to give their children food or drinks before Kiddush on Friday night, as this Halacha was instituted only for those above the age of Misva obligation. This is also the ruling of several earlier Halachic authorities (Magen Abraham, Mishna Berura).
Summary: Once Shabbat has begun even if one accepted Shabbat well before sundown, as many people do during the summer one may not eat or drink anything, even water, before Kiddush. This applies to both men and women. Children below the age of Misva obligation may be given food or drinks before Kiddush, though children approaching the age of Misva obligation should be trained to wait until Kiddush.