In your state, are minors allowed to drive without a licensed adult in the car? If not, then you may have grounds to sue. Or, if the driver was under the influence or driving recklessly, didn’t have a license, or for some other reason was not following the “rules.” Even if the driver was behaving responsibly, you might legally be able to sue. Whether or not you should sue is a moral issue and I think @JLeslie has a good idea. What if the driver had been your child? There really aren’t enough details in the question to know if legal action is required.
I don’t know if I’d try to punish the driver for the passenger not wearing a seat belt. Legally the driver may be responsible for passengers, and I’d leave it up to the police to determine who to ticket and who is at fault. We’re so “sue happy” in this country. I’d be mad at my own kid for not wearing a seat belt.