I've done that. One month in a 1961 VW panel van in 1972. I worked downtown and drove up into the hills each night.
More lately it's road trips, like to Bonneville. The Superbeetle had an L-shaped deck that was six feet long down the right side. It had a Koolatron in the rear storage compartment and a 12V outlet above the battery. It had a 110V converter but I never used it.
My latest acquisition is a little 12V coffee pot. $4 at Goodwill. I can sleep in the Dasher, as when I went to the Darko wind tunnel, but it's much harder to get in and out.