Is there any accommodation for rent available inside the airport for one night stay. We are travelling to India through Newark but coming from Illinois. Is quarantine must?

Yes quarantine is recommended for 14 days when traveling

No, Newark airport doesn't have any in-airport hotel accomodations. You will have to quarantine when you return from India, but I do not think they will care if you go to a hotel for one night and then come back for your next flight out of EWR.

https://covid19.nj.gov/faqs/nj-information/travel-and-transportation/which-states-are-on-the-travel-advisory-list-are-there-travel-restrictions-to-or-from-new-jersey Here's a list of states to quarantine from when arriving in NJ. Scroll down