Water intoxication happens when a person consumes large (unreasonalbly large) quantities of water in very short periods of time and does not take the time to eliminate through urination. That has actually proved fatal for a few unfortunate marathon runners and at leat one radio show contestant a few months back.
The key here is - no one is saying that you should take in unreasonably large quantities of water. It's actually the recommendation to all humans to drink this much in order to be properly hydrated in normal everyday life. Also no one is saying that you should chug all of this water at once. It is actually better to sip water throughout the day. Chugging is not encouraged. What is encouraged is elimination. This is a cleanse. It has been said many many times before that you should stick close to a bathroom - especially after the SWF. Which brings me to one other point - the SWF is very important to the MC. If you don't stay well hydrated, chances are - you will have problems with the SWF.
Adequate hydration is so important - don't skimp on your lemonades or your water - out of an unreasonable fear.