Maybe some placebo for some people? But there have been times where I couldn’t figure out why I was so energetic, only to remember that I had an extra cup of coffee or drank it later than normal.

I think most regular coffee drinkers know the simulant effect is very real. And I also think that, because of the sheer number of coffee drinkers over the last several hundred years, any significant placebo would have been rooted out by now.