I have been the family mule for years pulling all of our beach stuff across the sand one way or another, typically in a cart purchased for the beach.  My last cart even touted "wide wheels" for sand.  Well, the wide wheels were useless.  I even tried making my cart a "dually" by doubling up those wide plastic wheels.  Waste of time.  I then saw another brand of really great sand wheels but was too cheap to pay the big bucks for them so I figured all I need is a good inner tube with a custom rim.  Tried it and Eureka, the difference is absolutely ridiculous.  I can actually casually push my cart across the sugary sand of the panhandle instead of bending over and dragging with all my might.  So many people have asked me about these that I decided to pass this along.  I don't make much profit at all.  It's just a 3D printing hobby.  If you have your own 3D printer, give me a shout and I can try to work you up a file so you can print them yourself.