I used to get a bit nauseous before sparring but that went away with experience. It's possible that it's nerves.

Here's a bit of a weird question. What do you typically eat prior to going to the gym, especially on sparring days? How soon or not soon do you eat before sparring? The reason I'm asking is that I noticed with myself many years ago that if I consumed anything with a high acid content prior to strenuous activity (especially competing where I was nervous) I'd come really close to throwing up. I mean really really close.

Maybe diet may be at least part of the issue?