Running Spark with SSO on Windows 10 as a STANDARD non-local admin user WITHOUT creating a scheduled task, or using a 3rd party solution.
Simple fix is to install the Spark client in the C:\Users\Public\Spark folder. Worked like a charm. No UAC pop up or having to use a 3rd party solution or any additional workarounds. I followed the 28 Steps to Single Sign On for Openfire XMPP Server on Windows Server 2012 R2 with Spark documentation to setup SSO. ***The UAC issue does not affect Windows 7 clients, only my Windows 10 clients (I do not have Win 8 or 8.1 clients to test with).***