yes it is true. i did a report about it in high school. soda, coffee all have caffiene in it. they are both diuretics. caffeine pushes water out of the cell, and with creatine, you are wanting to volumize the cell. water is pushed in the cell. if you take caffeine while on creatine, it's like a neutral effect. water is being pushed out, and water is trying to be pushed in. hope this helps.