I'm with Puckster.  I have a couple of collapsible sinks but have never used them.  The only time soap is needed is when the food has enough fat in it to make the pot or plate feel greasy.  The first key is hot water, which melts the fat, and a drop or two of soap helps.  The second key is to rinse with filtered water.

You can also clean pots and plates with ... dirt.  That's right, dirt.  It's both abrasive and absorbent.  This method works even better using oak leaves and sand.  I "washed" dishes this way for years when I was using a cast iron frying pan to cook spam, eggs and pancakes.  If using dirt, it helps to rinse.  If using sand, there's no need to rinse, just wipe.

Uncivilized, you say?  My dad told me stories of poor kitchen sanitation when he was in the army, and he taught me the dirt/sand/leaves method.  Worked for him in the South Pacific, worked for me in Boy Scouts and car camping.