Wikpedia explanation of the LDS view of the Sacrament:
"Among Latter Day Saints (or Mormons), the Eucharist (in LDS theology it is "The Sacrament") is partaken in remembrance of the blood and body of Jesus Christ. It is viewed as a renewal of the covenant made at baptism, which is to take upon oneself the name of Jesus. As such, it is considered efficacious only for baptized members in good standing. However, the unbaptized are not forbidden from communion, and it is traditional for children not yet baptized (baptism occurs only after the age of eight) to participate in communion in anticipation of baptism. Those who partake of the Sacrament promise always to remember Jesus and keep his commandments. The prayer also asks God the Father that each individual will be blest with the Spirit of Christ.
The Sacrament is offered weekly and all active members are taught to prepare to partake of each opportunity. It is considered to be a weekly renewal of a member's commitment to follow Jesus Christ, and a plea for forgiveness of sins.
The Latter Day Saints do not believe in any kind of literal presence. They view the bread and water as symbolic of the body and blood of Christ. Currently The Church of Jesus Christ of Latter-day Saints uses water instead of wine. Early in their history the Sacrament wine was often purchased from enemies of the church. To remove any opportunity for poisoned or wine unfit for use in the Sacrament, it is believed a revelation from the Lord was given that stated "it mattereth not what ye shall eat or what ye shall drink when ye partake of the sacrament, if it so be that ye do it with an eye single to my glory — remembering unto the Father my body which was laid down for you, and my blood which was shed for the remission of your sins." After this time water became the liquid of choice for all Sacrament uses."
I'm impressed with this explanation, I think they did some very good research.