Preparation for a SIP order should include the following:

Gather supplies. The general recommendation in the emergency preparedness literature is that people should store enough food and water to last 72 hours. Those supplies will be more than adequate for a time-limited acute health crisis which is normally less than 24 hours.
There should be a supply of blankets to keep people warm in the event of a loss of heat, and fans to keep people cool when sheltering in hot weather. In addition, companies should store items to address comfort needs for employees. Items such as towels and hygiene products might be considered for addition in the SIP supply kit.