Fabreeze will work very well on places it reaches but also try this.  Place
several cereal size bowls on the floor of the van 3 or 4 will do.  Fill
with ammonia, the plain uncented type, close all the doorsand windows and
leave it that way for as long as you can, at least 3 days-obviously, don't
drive the van.  Throw out what hasn't evaporated and air out. Why this
works I don't know but was told about this by a pest control company when
Mickey did the dirt dance in our cellar.  It really works.

Good luck

PS, it also gets rid of stale cigarette odor or most any other for that
matter.