When you exercise you produce a lot of hormones (endorphins, vasopressins). The combination of these can make you nauseous.
Try to increase your cool-down time so all that blood that was being used in your muscles doesn't go back to working on digestion and bringing all that shotblock and Gu sugar back with it.

Drink a 50% Gatorade 50% water within 15 minutes to replace glycogen.

That's all I got.