Try to avoid vehicle living if all you have is a crowded cramped small vehicle. Try to have a cargo van. Even a passenger van such as a Honda, Toyota or Chrysler is better than a cramped small car or SUV.
But, if small is all you have it beats a cardboard box or tiny tent. Well, a tent in the right circumstance could be nice. If a tent is used as a bedroom and you have full access to a house that might be a fine way to get by in a sem-homeless manner.
This fellow only mentions sleeping in his SUV. No mention of storing clothing and other possessions or blocking windows for privacy. This video is presented here to show an option of using the rear cargo area and the rear passenger seat for the bed. Be creative with whatever you have to work with and use trial and error to find what works best for you.