Sandy soil drains very well; in fact it drains too well. Water rips right through before the plants have a chance to get a full drink, and there is little to no water retention because unlike clay, sand can’t hold water very well.
The solution is simple. You need to find every way you can to get organic material down into that sandy soil. There is no other way to deal with this problem. You work organic material into the soil when you start a lawn or a garden bed. You add organic material every time you plant a tree, shrub, or any other plant. Finally, you need to have organic mulch around all plants 365 days a year. In three to five years, your sandy soil will have become black loam.