Yeast is a living (fungal) substance, which must have something to live on. It can't survive on sugar alone, so your suggestion wouldn't work.
For a cheap addition to get it to work, just throw in a few spuds and then distil the resultant product. That, so I'm told is, how hooch is brewed in prisons. It's said to have one hell of a kick. The only downside is that as well as producing ethyl alcohol, there's a risk that bacterial activity will also produce methyl alcohol. The former is the psychoactive drug which you're aiming to produce, the latter is highly toxic.
Chris