Interesting idea, Mercurial.
Caffeine works by binding to and blocking the adenosine receptors in the brain. Adenosine is a natural brain neurotransmitter that helps induce sleep, so blocking it promotes wakefulness.
People who consume a lot of caffeine develop a tolerance effect. The best way to restore sensitivity to caffeine is to withdraw for a few days and to moderate the level of consumption. So withdrawal, in and of itself is a kind of hormetic "anti-caffeine" to some extent.
If you want to go further than that, you could look at ways to either increase adenosine levels, or perhaps upregulate adenosine receptors. Studies show that one drug, phenylephrine, a common antihistamine decongestant known to produce drowsiness as a side effect, does exactly that:http://ajpheart.physiology.org/content/298/2/H545
There are probably more natural ways to achieve this. I'd also have some concerns about anything that makes you excessively drowsy. I'll look into it further....maybe others have ideas?