People who start arguing about caffeine and Mountain Dew and why can we drink this or not that remind me of the lawyer in Luke 10:25-39
25 ¶And, behold, a certain lawyer stood up, and tempted him, saying, Master, what shall I do to inherit eternal life?
26 He said unto him, What is written in the law? how readest thou?
27 And he answering said, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy strength, and with all thy mind; and thy neighbour as thyself.
28 And he said unto him, Thou hast answered right: this do, and thou shalt live.
29 But he, willing to justify himself, said unto Jesus, And who is my neighbour? (New Testament, Luke, Chapter 10)
The lawyer new the rule, but then he wanted to impose restriction on it and see what he could get away with. Jesus calling his bluff then proceeded to give what is commonly called the Parable of the Good Samaritan wherein Jesus didn't give the lawyer a list of things he could or couldn't do, but instead gave an example of how one should treat another.you can read that it Luke 10:30-37
What is the point of Doctrine and Covenants section 89 otherwise known as the word of wisdom?
Is it just a list of Do Nots? No. It is instructions on how to keep oneself healthy and receive blessings in return. Written by Joseph over 100 years before people realized cigarettes were actually bad for us, before medical science started saying well actually people shouldn't drink too much coffee or tea or alcohol, that we shouldn't eat too much meat. Hundred years before nutritionists came up with the food pyramid showing we should eat grains and herbs and fruits. The word of wisdom follows the food pyramid exactly and yet the first was only created in 1974. Joseph was either a prophet or just extraordinarily ahead of his time.
Malachi 3:14 describes people who murmured about the commandments.
14 Ye have said, It is vain to serve God: and what profit is it that we have kept his ordinance, and that we have walked mournfully before the Lord of hosts? (Old Testament, Malachi, Chapter 3)
These people forget that a commandment from The Lord is a commandment from The Lord. People try to 'get out of being too righteous'. Like the lawyer they try to justify skirting around the law. People often criticize the word of wisdom saying things like "there is proven health benefits of a little wine, or in drinking tea or a small amount of coffee". Sure there is, I don't disagree. But those same health benefits can be achieved through other means.
The whole point of the wow is to keep our bodies healthy so The Lord can bless us spiritually. You need to make your own mind up wether you think it's okay to drink energy drinks or Mountain Dew. There is nothing any general authorities have said that we should stay away. But personally for me, I am not interested in either of them.
But remember, drinking coffee or tea is not the problem. Like Paul wrote in Galations 5:21 that rebelling against The Lord will drive away the spirit
21 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God. (New Testament, Galatians, Chapter 5)