damn i was gonna say meth but a large dose of LSD might be the way to go
tried a lot of drugs in my time and while i would never try and glorify taking any form of drug i can at least give you an idea of what heroin is like. spend 2 or 3 days heavily exercising and working your ass to the bone to the point of exhaustion. get zero sleep to the point where the most important thing in the world is to get 5 minuets worth. now go find yourself a nice comfy bed and go to sleep, the last few seconds before you fall asleep is basically what heroin is like.
if you've ever seen a junkie given a shot of Naloxone to bring them out of an OD and seen how pissed off they can get it's basically because they have been woken up from the best sleep they have ever had.
i also want to counter this post with the fact that i have spent a bit of time as a drug counselor and had numerous friends die either directly or indirectly from drug abuse and while it could be possible to try some of the more addictive drugs a few times and walk away before addiction takes hold every single person i knew that tried meth or heroin did eventually become addicted and spent years battling the addiction if they were lucky enough to survive.
i can tell you stories of people turning from high powered accountants to hiv positive prostitutes in months or how one dose of heroin made one guy rob his own grandmother in days but suffice to say