Weed only. Only when working on rough-draft/poc code. Oh, and making architecture diagram.
I can either see the big picture clearly, draw.
Or I see the narrow problem in detail. Crank that Boston+Rush playlist and code one component complete but rough.
Also, sometimes I've got to grind through managerial paperwork, so reefer there too.
When I moved to Seattle I learned of a "Northwest speedball" - espresso+weed.
Oh and I use alcohol at nearly every sales/networking function.