Restarting the Kiwi Syslog Service will always clear (uninitialize) the Global (and Custom) variables.
That said, please bear in mind that if you are running script tests though the Kiwi Syslog Manager, then it (Kiwi Syslog Manager) maintains it's own sandboxed versions of the VarGlobals. You will need to restart the manager in order to clear those.
If you want to explicitly uninitialize a Global Variable, add the following statement to the script:
Fields.VarGlobal02 = Empty
You may also want to use the isEmpty function to check for an initialized variable, instead of VarType.
If IsEmpty(Fields.VarGlobal02) Then