I think coffee is great. I often get coffee before I hit the practice rooms at my school. Can I consistently practice at the energy level that coffee offers? No. After all those sessions, when I'm completely sober, can I play all the notes that my practice added up to? Yes. I think insight is similar.
It doesn't matter if you're feeling shitty, great, high energy, low energy, enlightened or not. If you hit the A&P on vipassana, lucid dreaming practice, daydreaming, death contemplation, or LSD, you'll probably experience cycling through DN stuff to some extent, even if the moment it happened was a different context. I believe a similar thing applies to any insight stage, with any substance. If you can get to the stage of insight through concentration and investigate the 3 c's, you'll make progress, and getting paths is just a matter of getting ever more inclusive and precise with this technique. At least, that's my understanding of it at this point. This isn't just a cop out excuse for using any substance and claiming that insight can happen regardless of sobriety. I'd imagine that alcohol would make it hard to get a lot out of practice.
I like to drink coffee before doing vipassana. Coffee seems to make everything I'm doing more interesting and visceral, and I find that effect to be very useful for bringing a lot of energy to practice while still remaining curious.
EndInSight claims to have gotten 1st and 2nd path quickly using a practice formula involving a large amount of caffeine.Substances can be really taboo, but I'm very interested in how substances and practice could come together. Call me a typical hippie/teen/musician/whatever, but I think there's a lot of "enlightening" potential in substance use. In the last month, I've used marijuana, coffee, and LSD, and I've been able to access all (edit: the first) 4 jhanas and basically nanas 1-11 while under the influence of any one of those. I was smoking marijuana the day I got stream entry. I'm not a regular user of anything besides caffeine, and I don't claim that drugs can singlehandedly unlock new territory or offer a huge advantage in practice.
Interesting though: in going through the nanas, our experience changes so rapidly and dramatically. Is there some reason that heavily "altering our state", "altering our perspective", or altering our perception of sensations in this way can lead to enlightenment? How does coffee play into your perception of sensations?
I realize that this post probably goes a little bit farther than what you were asking for, but I figured I would write out what came to mind. You also inspired me to write
this goofy thread.