Inserting variable in command string

Ahh, what you'll find is that your $sid variable doesn't actually contain what you're expecting it to contain.

The way it's being used you're wanting it to be a string of just the SID, but it's currently an object with one property. (Seems like a nitpicky distinction but id does have implications in situations like this.)

If you call $sid, what you'll see output atm is:

SID
---
S-1-5-21-7375663-6890924511-1272660413-2944159

but what you actually want is just

S-1-5-21-7375663-6890924511-1272660413-2944159

All of that is to say, either change this line:

$sid = Get-Aduser -identity $user | select-object SID

To

$sid = Get-Aduser -identity $user | select-object -ExpandProperty SID

The -ExpandProperty option "expands" the select property such that it's the new "Object" being returned, rather than selecting child properties of the parent object. Basically it means you just get back a string...

And alternative to that approach is:

$sid = (Get-Aduser -identity $user).SID

Which pulls that property out and has much the same effect as the expandproperty.

One final option is to reference that property directly inside the Invoke-Command scriptblock:

$($Using:sid.SID)

This method actually opens up a few posibilities. For example, if you got rid of the select-object and did something like

$UserObject = Get-Aduser -identity $user

Then you could reference the sid when needed:

$($Using:UserObject.SID)

But elsewhere you could also use the other properties:

$($Using:UserObject.SamAccountName)

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Sorry that was a touch long winded, just wanted to fully playout the problem and potential solutions