Perhaps the single most notorious characteristic of the vampire is his penchant for drinking blood. Most dead creatures (ghosts, demons …) in the Indo-European and Semitic world are considered thirsty, not just vampires. While some dead were content with any liquid offered, vampires almost always choose blood.
Throughout history the many liquid substances (milk, honey and wine) offered in sacrifice to the dead, to spirits and to gods, were symbols of blood. Sacrificial blood was itself obtained from animals in classical times, and from human sacrifice among Asians, Africans, aboriginal Americans, and from prehistoric Europeans.
Alan Dundes (The Vampire; A Casebook) suggests that aging and dying are correlated to dehydrating; the same way a ripe plum shrivels into a prune. He further hypothesizes that people, therefore, assumed that the dead would be thirsty since they are dried out. This belief led to the practice of pouring libations on graves to appease the dead. This belief was later applied to vampires who went looking for their offerings.
Another answer is that the dead's craving for liquids is not merely to regain the appearance of youth, but to give them life again, blood being the supreme elixir of life.
Blood both fascinates us and repulses us; it simultaneously represents purity and impurity, the sacred and the profane, life and death. Little wonder then that it is heavily used in religious, magic rituals as well as art creation where it is often associated with the violence of sacrifice, whether as an offering, a punishment, or atonement.
Ritual sacrifices worldwide have been predominantly blood sacrifices; it is with blood that gods are bribed, appeased, or enlisted in human enterprises, as hunting, farming or war. For the Inca of Peru and the Aztecs of Mexico, (human) blood sacrifice ensured cosmic regularity; for the Israelites, blood sacrifice established and maintained the covenant of God with his people. In each case, ritually spilled blood reinstates or ensures the continuation of order (fertility) and proper human relations with the gods or God.
When shamanism is associated with women, blood letting during menstruation is an important part of 'walking with the spirits'. Followers of the cult of Kali in India often drink blood. Sisir Das, a practitioner of Hindu occult rituals, drank the goats' blood of 207 sacrificed goats at the Kali temple in Bengal's Midnapore district over the course of four days.
Among the Germanic tribes (such as the Anglo-Saxons and the Norsemen), blood was used during their sacrifices; the Blóts. The blood was considered to have the power of its originator, and, after the butchering, the blood was sprinkled on the walls, on the statues of the gods, and on the participants themselves. This act of sprinkling blood was called blóedsian in Old English, and the terminology was borrowed by the Roman Catholic Church becoming to bless and blessing. The Ancient Greeks believed that the blood of the gods, ichor, was a substance that was poisonous to mortals.
In a similar fashion, the history of art is full of images of blood, from the representations of wounded animals in the cave paintings of Lascaux to the most recent representations of extreme Body Art.
In his book 'Violence and the Sacred', Rene Girards' theory of sacrifice states,
"The physical metamorphoses of spilt blood can stand for the double nature of violence...Blood serves to illustrate that the same substance can stain or cleanse, contaminate or purify, drive men to fury and murder or appease their anger and restore them to life"