Never use tobacco products, such as cigarettes, snuff, chewing tobacco, cigars, and pipe tobacco. They are very addictive and will damage your body and shorten your life. Also, do not drink coffee or tea, for these are addictive and harmful.
Any form of alcohol is harmful to your body and spirit. Being under the influence of alcohol weakens your judgment and self-control and could lead you to break the law of chastity or other commandments. Drinking can lead to alcoholism, which destroys individuals and families.
Any drug, chemical, or dangerous practice that is used to produce a sensation or “high” can destroy your physical, mental, and spiritual well-being. These include hard drugs, prescription or over-the-counter medications that are abused, and household chemicals.
Even with this clarification, members of the Church have sometimes wondered whether caffeine is or isn't prohibited by the Word of Wisdom. At least two prophets have commented on this matter. In the April 1922 General Conference, President Heber J. Grant said:
I am not going to give any command, but I will ask it as a personal, individual favor to me, to let coca-cola alone. There are plenty of other things you can get at the soda fountains without drinking that which is injurious. The Lord does not want you to use any drug that creates an appetite for itself.
President Kimball said something similar:
Wisdom goes beyond the letter of the law. Generally when we speak of the Word of Wisdom, we are talking about tea, coffee, tobacco, and liquor, and all of the fringe things even though they might be detrimental are not included in the technical interpretation of the Word of Wisdom. I never drink any of the cola drinks and my personal hope would be that no one would. However, they are not included in the Word of Wisdom in its technical application.
I quote from a letter from the secretary to the First Presidency, 'But the spirit of the Word of Wisdom would be violated by the drinking or eating of anything that contained a habit-forming drug.' With reference to the cola drinks, the Church has never officially taken any attitude on this, but I personally do not put them in the class as with the tea and coffee because the Lord specifically mentioned them.
Thirty years later, the Church still has not taken an official position on caffeine. They have, from time to time, warned of its dangers in Ensign articles or passing comments in local conferences, but the ultimate choice is left up to the members of the Church. It is then our responsibilities to be good stewards, making choices that will lead us back to our Heavenly Father according to the dictates of our own inspiration and conscience.