Yeah. Not on the side where an outside cooking area would be, though.
When I remade the kitchen counter (I replaced the double basin sink with a single basin and got tons more counter space) I had enough laminate left to make a nice sized shelf.
I mounted it on the driver side near the outdoor shower with this table bracket:
https://www.dyersonline.com/ap-produ...SABEgKp0PD_BwE
We wash all our dishes out there using biodegradable Castile soap. Many of the campgrounds we use have waste water disposals for the tent campers. We use them, too. The shelf is also a great spot for shaving or a quick face and underarm wash in lieu of showering. Being next to the outside shower there is hot and cold water.
A shelf would work on the passenger side. You would just have to carry water to the tubs from the kitchen sink. If you put folding supports under the shelf (like you can see in the bottom photo) you won't need to worry about weight.