Evaporative coolers, sometimes called swamp coolers, are an option in areas with low humidity. They do not cool by a certain number of degrees, but rather output air ~5-7F above wet bulb thermometer reading. Standard sizing is cooler cfm = cubic feet of area / 2.¹⁾

Water consumption for a van-sized space is about 1 quart/hour of cooling.²⁾

The main manufacturer of RV swamp coolers is Turbokool.

Portable units are not a perfect fit for 'dwellers since they were made for stationary use.

If you go his route, don't install any rollers that come with the unit, and restrain the cooler safely. Since small coolers put out relatively little cold put it somewhere it can blow air directly on the areas you spend the most time in.

Units with electronic controls should be run off pure sine wave inverters.