Why do we have little sweat bees hovering around the deck at the back door?

Answer 1

These little bees/wasps like sweet items.
Are there Hummingbird feeders nearby? There is an easy way to get rid of them without spraying. In a glass jar, mix about 2 spoons of sugar into a cup of water and stir well. Tape almost the whole top area, leaving only a tiny spot- enough for the bees to enter.
You should be able to trap them all. Use Duck Tape because it's difficult for bees to chew through.

Answer 2

I have seen them digging little holes into wood to lay their eggs. It is possible there is a nest nearby.