'Tis very confusing - especially when you've been around as long as I have, and have seen the rules change so often.....sigh.
I think a really good way is to have the minimum 2.25 litres/4 pints as plain (or fizzy) water, with anything on top as "flavoured" water - teas, coffees, CD flavourings***, etc.
I hope you all know about the Diet Sandwich? - big glass of water before and after each CD portion, which really helps to get through the water requirement more easily.
Our bodies really like water little and often. Think of a houseplant: pour a pint of water into it, and most will flood straight through, whereas if you drip the pint in bit by bit, the plant stands a good chance of using most of it. Same with bladders, methinks.
After all these years of practice, I have no problem drinking 6 litres of water a day - but I am 5'10".
***But don't get me started on the Golden Veg water flavouring - main ingredient is salt, and salt, of course, must not be used in CD soups.....I am waiting for it to be discontinued....