Invalidate session

Hi there,
Using SGW & mobile on PC(s), creating a office intranet with Session auth.

So we present user with login modal, then we POST to the public Api to the Session endpoint with un/pw - we successfully get back SGW Session ID, Path & Expiry. All working great.

To test the Login Dialog I would like to invalidate the Session ID (to test if our replicator error handler works & shows user login modal again), how can I do this?

I considered using ttl but that only works on the Admin Api and if I read other post correctly reads once on first request , so no good.

Any pointers appreciated. Thank you