The Word of Wisdom doesn't speak directly of caffeine, colas, etc. It is an area where each member regulates him or herself within the guidance of their own conscience. There have been warnings of too much can be bad, while others point out that caffeine is addictive. but officially speaking, it is coffee, tea (except some herbals), alcohol, tobacco and illicit drugs. The Word of Wisdom, however is not only a prohibitive commandment, there is also guidance given on what foods we should look to for good sustenance.
If you're interested, I'll link you the actual citing for it.