Coffee and caffeine pills. If those don't work like they used to, then its probably a manifestation of a larger issue (not going outside, poor hygiene, etc). I don't have anything against people who use more advanced substances, but I've found roughly the same effect as caffeine pills.
Green tea in the morning. Espresso after lunch. Maybe another tea at tea time, Earl Grey, hot.
Caffeine and, occasionally, L-Theanine. I have dabbled with using 5-HTP a few times.
1. coffee a few times a week
2. alcohol occasionally
Walking and thinking constantly
Have to ask, do you consider those substances or did you not notice that part of the question?