All of my vehicles have fabric upholstery so I don't need anything special.
I have a 2gal pump sprayer and my shop-vac that I use to clean the insides every year or two. I spray everthing, starting from the top and in sections, with a diluted cleaning solution. After I have everything cleaned I go back over it with a clear water rinse. I have been known to use the garden hose for the rinse. Some grease or spills require brushes and multiple spot cleanings.
After everything is cleaned and rinsed I just roll the windows down and leave it out to air dry. Sometimes I'll drag the big shop fan over, open both doors, and blow it in one side and out the other in the sunshine.
It really does a heck of a job.