I lived in a Honda civic for ~2 months in Oakland/Berkeley, and am semi nostalgic about it now that I have a regular housing situation. I would usually mess around at a late night cafe until ~11-12, use the bathroom, go setup car for sleeping and then drive to a good spot. Wake up and go straight to the gym, light workout, sauna, shower, bam ready to go before 8ish. The main downfall was that I am 6'1 and a civic is not ideal for comfortable sleeping.

If you really want to try it though just do it some night, I started by just folding the seat down and putting a sleeping bag and pillow across it. It is pretty uncomfortable, but the absence of repetition really slows time and makes each day seem more vivid. Also if you have any qualms about using public restrooms you will get over them real quick.