I have an extra large mug and I have my tea, coffee and shakes in that. 4 of those a day is 2.5 litres of water so I only need to drink half a litre of water on it's own a day. Luckily, I take my tea and coffee really strong so they only have a tiny splash of skimmed milk in. I have my shakes hot too with 600ml of water. If it's tastes a bit too weak then I pop in a sweetener but havent really needed it x