Remove the UltraStream. Dry out as best as possible draining the hose. Than remove the spout on the top, invert and drain in a sink for a few hours. You can also dry it in the sun while inverted so it also drains.
We’ve found it helpful to blow threw the diverter pushing the water out the top while inverted. Wrap it in “cling plastic wrap” and store it in a refrigerator. When re-installing, run for 20 minutes to flush it out.