It works most of the time, but it doesn't work if you are drinking alcohol... your body has to 'waste' water to flush it out of your system. There are probably

It works most of the time, but it doesn't work if you are drinking alcohol... your body has to 'waste' water to flush it out of your system. There are probably other drugs and medications that have the same effect (and no, caffein is not one of them, at least to my knowledge).