Just saying we can tweak the nation somewhat to make it semi-sustainable. I've mentioned the great river we can include in it and we can make it where they can convert sand into some ore and wind into energy. Anything.
The Great River? There's a Sea right outside its borders, I honestly don't think they need a River they just need common sense. It should not be hard for them to get a steady supply of water from a Sea the size of a whole dam country.
They have gold and rare herbs, but it's not uncommon for there to be deposits of iron, oil and natural gases beneath the sand.
Sand into ore is...iffy? I suppose if they used ninjutsu they would be able to, but you run into the same problem I told Shen about the Yuki farming. Ninja is somewhat stuck performing duties that the normal people simply can't because Ninjutsu is
too effective and a single Ninja would displace tens of normal workers.
There's sandstone though, which could be used for something.
Wind Energy is a thing, oil is the better option though.