Nothing.

I can do exactly nothing while you're sitting there.
On that stool.
Minding your own business.
Drinking beer so dark, I can't see through the glass.
Well that's not true.
I can sit here on my stool, and be uncomfortable.
I can be awkward.
But I can't talk.
Can't think.
Can't even breathe.
I can't drink or make alluring movements with my female body.
I pay my tab, then get up slowly to leave.
You nod at me or maybe shake my hand.
It doesn't always have to end like this.
I could be familiar in a different way.
But your eyes have already moved back down to your glass
or your friend sitting beside you.