"He could sell sand in the Sahara desert”—meaning that he can sell something to someone who has no need for it—is an old expression to show that a person is a good salesman. “The kind of genius who could go out to the Sahara and sell sand to the Arabs” was cited in print in 1913.
“He could sell ice to an Eskimo” is a similar saying.
2 September 1913, The Evening Star (Washington, DC), pg. 6, col. 3:
From the Boston Transcript.
The Washington lobbyists who admits that he had been making a good living selling public documents grafted from congressmen is the kind of genius who could go out to the Sahara and sell sand to the Arabs.
29 August 1918, The Daily Capitol News (Jefferson CIty, MO), “Social News,” pg. 2, col. 3:
“I believe this crowd of beauties could sell sand in the Sahara desert or sunflowers in Kansas,” she continued.
15 June 1919, Augusta (GA) Chronicle, “Southern Tire Company To Be One Of South’s Big Industries.” pg. 4, col. 2:
But, as the old saying goes, “his neck was bowed,” and Weems Smith went to it with a vim, such courage and enterprise that would enable a man to sell sand in the Sahara desert, and he has “put over” the Southern Tire Company.
September 1919, Boys’ Life, “The Animal Gets Even,” pg. 44, col. 2:
“You’ve as much chance to sell ‘em to this old goat, as you’d have to sell sand to an Arab.”
17 August 1920, Syracuse (NY) Herald, pg. 6, col. 8 ad:
Some waiters are so persuasive theycould sell sandbags in the Sahara!
(The Kirk Stag Restaurant.—ed.)
27 May 1922, The Evening Star (Washington, DC), “Mutt and Jeff” comic strip by H. C. Fisher, pg. 12, col. 2:
MUTT AND JEFF—Jeff Could Sell Bridges in the Sahara Desert.
23 February 1926, Evansville (IN) Courier, “Paragraphy” by Jroy, pg. 6, col. 2:
Tom Morgan called us in to hear the latest song hit. It wasn’t for sale, he said. We listened to it and bought it. That bird could sell sand on the Sahara desert.
Big shout out to #ChrisBox & #JamesWarburton they could sell sand at the beach!
12:39 PM - 13 Aug 2015
@SupremeRair dummface retweeted XXL Magazine
This is just a yeezy in a different color way. But whatever. It’s Nike. They can sell sand in a desert & sell out. dummface added,
XXL Magazine @XXL
The newest Nike Air Cruz colorway gives a nod to the NY Giants:
3:27 AM - 14 Aug 2015