Here's an idea for using hugelkultur in sandy soil.
Ideally for sandy soil you'd want lots of rotten wood dug in for water retention.
However, if you only have dry (not green) unrotted wood available, you could still get benefits from hugelkultur right away.
Bury stumps, branches, split firewood, vertically in the ground about 3-4" below the soil surface.
Then plant right over the buried wood. The plant roots should grow down underneath the wood. The wood will retain a lot of water and slowly "drip" it out the bottom unto the roots, feeding them with a decomposed wood stream and any fertilizer you add (urea, urine, bloodmeal, fishmeal, ...). This is what I observed in "stump containers". See:
Overtime as the wood rots it should hold even more water and since it is large chunks of wood, they won't wash away deeper into the sand with rains.
My own soil is clay, so I've never tested this, but just thought about it after visiting my parents in sandy soil Florida. I would not do this in clay soil. In clay soil, I bury the stumps about 1' under the soil surface. The stumps wick away excess moisture without drying out the soil. Underneath stumps in clay soil, it gets very wet. In the 1-2 inches right underneath a stump in clay soil, I found, that roots will not grow, because it is so wet & mucky.