Happened to me yesterday. I was riding and began to feel nauseous and not dizzy but not well either. I made it to my destination and tried to pull off a slow speed left turn in the driveway, I didn't make it, it stalled and I hit the ground fast! The crash bar saved the bike but not fun. I lifted it up and just sat there for a while. No more riding while feeling ill. I went in to my friend's house and a bit of ginger ale cleared me up in about a half hour, rode home okay.
Gotta practice slow speed maneuvers. Time to do my RLAP (ride like a pro) exercises...