FWIW I did an 11.5hr ride on Saturday, and drank the following:

5 cans sport drink (Aquarius)
1 can Coca Cola
6 bottles mineral water (@500ml each) (approx – some of them I drank straight from the bottle, some got dumped in the Camelbak. Might have been more.)
1l from the Camelbak before I started refilling.

About 6l in total, roughly half a litre an hour.

It was warm – max about 25C – and near the coast so humid. Not as bad as Madrid in summer, but bad enough. Lots of hills, too – 165km and over 3000m climbing.