I was going to respond to the OP, but I only knew how an inner ear imbalance causes dizziness, not how said dizziness triggers the vomiting reflex. Thanks!
For those who want to know, there’s fluid in your inner ear and receptors that can detect where the fluid is, as well as where it ends (it’s surface). Your brain uses this system like a level to determine your head’s orientation to the ground, and if something fucks with the fluid in a way the brain can’t make sense of, you feel dizzy (the sensation of not knowing your orientation to the ground).