There are a few things not mentioned in the book that that have now become pretty standard from the collective wisdom experiences shared in forums like this.
The rule actually applies to every day regular living but many have found it of great benefit to continue on while MCing. Personally I can't follow that rule while MCing unless I wanna live near a bathroom. For me what works is drinking equal amount of water as lemonades. and even then if I'm out and about I gotta cut back some. I've taken to carrying a wide mouth empty bottle in the car while MCing in case I get caught in traffic. ;+D
Bottom line though is that through the collective experiences around here is that one should drink water in addition to the lemonade and my personal recommendation is to try and do equal amount to lemonade and if you feel you can do more and still function away from the bathroom then by all means go for it.