A liter an hour? That's a LOT of water.

I drink a bottle an hour on mildly hot days (in the low 20s Celcius) and that's about 600 ml. More if it's really hot. Less most of the time (maybe 3/4 of a bottle an hour).

I get nauseated when my sodium is low, tomato juice always fixes that. Maybe you're also bordering on hyponatremic (low sodium - can kill you fast if taken to an extreme)?