Fortunately for the bees in the back of my yard, I have several water gardens. The bees can stand on the edge of water lily pads to suck up water. There is also the "bird bath" I put out years ago, which has become a major watering hole for bees. On hot days there is quite a line up all along the edge. I put rocks in it to help bees get out if they fall in. Bees are very poor swimmers and drown rather quickly if they can't get a hold of something to pull themselves out.
This watering hole is a great place to see the variety of honey bees from the hives out back and from other places in the surrounding area. Some are the typical golden honey bee with tan fur and some are quite dark with grey fur like the one below. The bee on the left above is almost entirely black.