Members of The Church of Jesus Christ of Latter-day Saints obey a Word of Wisdom which is a few basic dos and don’ts given to us by our Heavenly Father pertaining to what we should and should not eat and drink for our own spiritual and physical well-being.
In 1 Corinthians 3:16 we read: Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?
Our Word of Wisdom is recorded in our scriptures. See Doctrine and Covenants section 89.
Basically, we abstain from smoking tobacco, using illegal drugs, drinking alcohol, coffee, black and green tea (herbal tea is acceptable). Meat is to be eaten “sparingly” (individual members define what that means to them). As for everything else, we follow the rule of “all things in moderation” (this includes caffeine).