Here is a quick tip to swap between Mount Sinai and Elmhurst Haiku on your phone (iOS):
Go to settings and search or scroll down to Haiku

Under “Connection Settings” input the following “Server” and “Path” inputs for the respective site.
Mount Sinai
Server: epicsoapproxyprd.mountsinai.org
Path: interconnect-haiku-prd
Elmhurst
Server: epicproxypda.nychhc.org
Path: hhc-haiku
Now you’re ready to re-login to Haiku and access the correct Epic!