To stop the Egnyte Desktop Sync application from starting on machine, simply move the file com.egnyte.egnyteSyncApp.plist out of the LaunchAgents folder of your Mac.
Note: By default, this folder is hidden. To access hidden folders, you'll need to navigate to Finder, select Go from the menu, and hold down the Option (Alt) key. This should allow you to access the hidden Library.
To resume startup of the application on boot, simply move the com.egnyte.egnyteSyncApp.plist file back into the same directory.