It's been taken for granted that Mormons don't drink coffee, tea, or any soda pop containing caffeine. Or do they? Of course, not all Mormons follow the rules all the time, but what are the rules, exactly? The restrictions in diet came from founder Joseph Smith himself, who received a revelation from God in 1833. The Words of Wisdom explained what was to be eaten and drunk.
But there was one contentious line in the Word that continues to inspire debate. “Hot drinks,” Smith wrote, “are not for the body or belly.” This appears to refer to tea and coffee, both popular beverages in 1830s America. Some modern Mormon scholars have argued that this is because these drinks are often served at near-boiling temperatures, causing a detrimental effect to both the body and the teeth. But others wonder if “hot” refers instead to the caffeine in tea or coffee, citing an 1828 Webster’s definition of “hot” that gives “stimulating” as one of its meanings.
That leaves a lot of room for interpretation. Would decaf coffee be considered a "hot drink"? Hot cocoa? Then Coca-Cola was invented years later -it's not served hot at all, but it did contain a small amount of cocaine at the time. And when the cocaine was gone, the caffeine remained. The disagreements about what drinks are prohibited continued over the years, and led to the story of the secret vending machine that held ice-cold bottles of Coca-Cola and other soft drinks at BYU, which you can read at Atlas Obscura.