By means of filtration. Put filter paper in a funnel. When you poor the water/sand mixture in the funnel, the sand will remain in the paper, and the water will go into the container.
How Can We Separate Sand From Water?
We can separate sand from water by many methods. One of them is Filtration technique. We can also use evaporation technique. If we keep the mixture of sand and water in sunlight, the water will get evaporated and only sand is left.
Heat pot with mixtures and carefully remove sand.