Coffee and Religion
Dietary rules and restrictions are a common part of many world religions, and usually involve the avoidance of various forms of meat (pork or beef, typically). But in a few instances, coffee and tea do fall under some religious restrictions.
The only time when coffee is restricted for Muslims is during Ramadan, a month of spiritual fasting. From dawn until dusk, no food or drink is allowed, even water is forbidden. It's pretty clear-cut, with no gray areas.
Latter-Day Saints (Mormons)
The LDS restrictions involving coffee are fairly well known, though I'm sure most people don't really know the details behind it. Coffee is specifically prohibited, as written in the Word of Wisdom: "Hot drinks are not for the body or belly" (D&C 89:9) It has been interpreted by the Church that Joseph Smith was referring to coffee and tea with this statement, as they are the only hot drinks commonly available at the time (early 1833). Some LDS members feel this is based on caffeine content, and then also feel that all caffeine is to be avoided. Some feel that the rule should be taken at face value, and therefore only refers to coffee and tea. The LDS church has no official position about caffeinated products other than coffee and tea.
There are no specific rules against either coffee or tea in Judaism, except for the broader rules of kosher eating. Both tea and coffee are kosher on their own, but there may be many other considerations to remember when enjoying your cup. One is flavoured coffee. Whether you are using flavoured beans, or adding syrups, you cannot be sure the kosher status of the many ingredients used to make these products. Many syrup manufacturers do offer kosher certified products. Another kosher issue can arise from decaffinated coffee. Ethyl acetate is one chemical often used in the decaffination process. One component of ethyl acetate is ethanol, which comes from grain. This would make coffee processed this way not kosher during Passover. There are several other aspects of coffee that fall under kosher rules.
The Seventh-Day Adventist's believe strongly in the importance of a healthy and wholesome diet, free from alcohol, narcotics and other stimulants. Caffeine was once officially prohibited, but no longer. It is still recommended that caffeine be avoided.
Like the Seventh-Day Adventist's, the Rastafarians follow a pure and wholesome diet. This excludes coffee, alcohol, salt, tobacco, meat and other processed foods. The foods eaten by Rastafarians (grains, fruits, vegetables) are all "ital" foods.