You can often sell a car without insurance. However, the vehicle should satisfy all of your state liability requirements, which may include taking the license off the vehicle and, of course,not driving it. You should make the buyer aware that the vehicle is not insured and they should only drive the vehicle if their own insurance coves it.
Each state is different so please contact an experienced broker in your area.
Disclaimer: The preceding answer should not be considered legal advice or binding in any way. It is simply an opinion.