Car vacuums can be dry or wet/dry.  The major benefit of wet/dry vacuums is that it allows you to clean solid as well as liquid mess easily. The next time your kids spill water or some soft drink in the car, you could grab the wet/dry vacuum cleaner to pick up all the trash smoothly. The moisture in your car can become a breeding ground for microbes. So, invest in a vacuum with dry/wet features and clean all sorts of debris quickly.