Shaggy, you talk of these volatile compounds that you huff for a quick trip and yet you're set on whacking carbonyls everywhere. I'll give you some examples.
Amphetamine: 11.3C mp, 203C bp
Methamphetamine: 3C mp, 212C bp
Ephedrine (beta-hydroxy methamphetamine): 188C mp
Noradrenaline (beta-hydroxy phenethylamine with some more hydroxyls): 217C mp, 442C bp
Admittedly these are hydroxyls and not C=O s but just chucking on Oxygens increase intermolecular forces, increases boiling point, decreases volatility.
Now, Nitrous Oxide and Xenon are both gases at room temperature and both have a fairly short lasting high. I think I read Xenon can last up to 30 minutes but can't confirm it.
Fragrances tend to smell nice, so amines are out along with thios. This automatically means we aren't looking for alkaloids. THC, CBD, alcohols (GHB/GBL/EtOH) and Salvia don't have Nitrogens. They're the only ones I can think of right now. Salvias pretty short lasting, weed gets you stoned for a couple hours tops when smoked, yet hours on end when eaten. Maybe this is a way forward?
But wait! Alas, your beloved Myrecene almost matches up with LSD's semi-backbone. With just an extra Carbon in that Myrecene, it would fall perfectly on top (ignoring the amide's N)
I don't think closed ring bk-DMAA is closed enough, maybe we need this
My only worry with this is that it closely resembles LEGO, and I wouldn't like to swallow those sharp pointy edges.
Offtopic here but why do cokes esters not just hydrolyse in acidic conditions, or is that why coke is shit orally and not any other route?