You don't need to drink 2 litres (whatever happened to pints) of water a day on top of your normal fluid intake. As explained in that great book, "Global warming and other BB*ll*cks". You do need around 2 litres of water total. So... that coffee, tea, coke, beer potato, curry etc all count towards your total.
On a run I count on 1/2 litre per seven miles.