The limits aren't wrt water absorption, but gut tolerance of sugar.

I get about 100g of sugar into a bottle by doing roughly 50:50 Gatorade and maltodextrin, and then throwing in some extra Na an K salt if it's going to be hot. Although with the super hi carb stuff you should make sure that you have some plain water as well - it sucks to be super thirsty but only have carb drink on the bike.