There are a lot of myths out there about the rules of Mormonism—Mormons can't use mirrors, can't wear makeup, and can only ride bicycles. All of these things are untrue, but Mormons do abide by a lot of rules laid down by their church. This list is full of activities banned by the Mormon church.
Mormonism is just like any other religion, in that there are rules about what you must do and must not do in order to cultivate your relationship with God. Some of these rules might be considered sexist or otherwise prejudiced, but those rules are not all that different from the rules of many other religions. These things banned by Mormonism ultimately shouldn't be too surprising.
Take a look at what it's actually like to be a member of the Latter-day Saints. You wouldn't be able to do any of these activities Mormons have banned.
Drinking coffee and tea is forbidden by the Mormon Law of Health, also called the Word of Wisdom. According to the Mormon faith, God spoke this law directly to Joseph Smith, the founder of the Mormon Church. Those who abide by this law are supposed to have good health, and will be better able to connect with God.
Smoking or chewing tobacco is prohibited by the Word of Wisdom. In fact, the Word of Wisdom came about because Joseph Smith's wife was disgusted by the fact that Smith and his fellow church leaders constantly chewed tobacco and spit on the floor. The complaints of his wife led Smith to ask God whether tobacco was appropriate for followers of his church to use. God said "Nope."
The last important component of the Word of Wisdom is the prohibition on using illegal or recreational drugs. This includes prescription drugs for which the user does not have a prescription.