Actually you want to give your system a rest while you sleep and you also want to get the best night rest possible cause thats when you body does the most healing so I would encourage you to not drink much of anything later in the evenings.
I go nine serving a day and I premix it all first thing in the morning and put it into 3 qt Nalgene bottles with sports spouts and put them in a collapsable cooler with some of that reusable blue ice things and take it with me everywhere I go. I petty much just sip troughtout the day and it works out just right for me.
Try pre mixing up 6 drinks (aprox 2 qts) and make yourself drink it throughout the day. You should also be drinking water. Mr Burroughs only recomends "extra water if desired" in the book so if volume of liquids is the problem then I would make it all lemonade to do at least 6 portions a day.
If you have problem with this small volume of fluids and in your regular daily routine you only drink like 32 oz of water a day I would bet heavily that many of your ailments if not caused by dehydration are certainly made worse by your lack of water in your daily life. If you eat lots of proccesed food, sugar, red meat, dairy etc in your daily life then those things will be major contributors to your toxic condition even more so with low daily water intake.
You should be able to greatly dimish or totally get rid of you ailments through cleansing ,nutrition, making sure you're well hydrated and getting regular exercise so I encourage you to look into the different cleanses in the site, particularly the liver/gallbladder flush and colon cleanse.
One of the best investments you can make is to buy a juicer and start drinking fresh veggie juices everyday. Drinking 16 oz of veggie juices a day will prolly equal the nutrition of 20 or more lbs of whole vegetables. Add to that that you can start using veggies that address your particular ailments.
The Master-Cleanse is a great "1st step" towards health but it is only one small part of the bigger picture.