What a great remark Brad!
Studies can never cover all the aspects of an issue, since everything affects everything. Therefore, we might get a bit confused about some controversial research results. Coffee and tea containing caffeine may work as mild diuretics in your body, but it depends, for instance on the amount consumed and your tolerance to caffeine. If you're accustomed to drinking coffee or tea (those containing caffeine), those drinks probably have a very mild or no effect at all to your hydration level. However, people tend to consider coffee and tea as powerful diuretics, then try to offset this effect by drinking a lot of water --> extra liquid to the kidneys and, therefore, more visits to the bathroom. I wish I could give you a straightforward answer to your question, but when it comes to the functions of the human body, it's not all that simple! 😄