Is it illegal to park and sleep in your car here?

I don't know but u can ask to the manager

If you park as close to the roads as possible for a night or two, I'm sure you'll be fine. But as Paul mentioned, you should ask them.

I don't know Meijer's policy on sleeping in your car. You could ask at the the customer service desk. I know Walmart allows ppl to spend the night. That's an option. Good luck