You cannot buy happiness, but you can buy productivity. Some things (all Amazon affiliate links which means if you buy anything on these links via below, I get around a 5-7% kick-back):

1. Coffee. Wink coffee (light roast) is great. I just grind it at home with either my mini stainless steel Porlex grinder (thanks Jun) or just using a random Nutribullet grinder (I do not believe in these stupidly expensive fancy coffee grinders). I also am a huuuuge advocate for the Clever Coffee Dripper (Cindy and I bought ours in Vietnam 3 years ago, traveled the world with it, and still use it [several times a day] here in the states). Clever is great — best hybrid between pour-over and the thickness of espresso. I drink lots of black coffee (no milk, no cream, no sugar, no silly almond or other pseudo-milk things) and water during the day to maximize my creative productivity.
2. 100% cocoa powder: I like the ‘Viva Natural’ 100% cocoa powder (no sugar) to give me a mid-day boost. I drink it just with boiling hot water. It acts as another good creative stimulant to me.
3. Matcha green powder: This stuff is very strong and potent. MatchaDNA seems to work well, and just a tiny bit of it (like seriously a very little amount) gives me a strong buzz. Careful with this stuff; I once drank too much powder, and I got really nauseous. The good thing with matcha green tea — L-Theanine + caffeine (good buzz).

No cocaine, no other caffeine pills, or weird stimulants for me.

The dosage is the poison. Drinking coffee is good because I cannot easily “OD” (overdose) on coffee. Compare it to Fentanyl (even 2mg, which is smaller than a penny can kill a grown man). According to this article, the average lethal dose of Fentanyl was ~10 ng/mL. You can read the New Hempshire PDF report on toxic doses of Fentanyl.

Postmortem levels of fentanyl confirmed in our sample range widely from 0.75 to 113.00 ng/mL, with a mean of 9.96. We compared the distributions of fentanyl levels for cases where fentanyl was the only drug found with cases with key co-intoxicants (opioids, benzodiazepines, or alcohol); the distributions were not statistically different. The distribution of fentanyl levels among the subgroup of decedents who reportedly had a “rapid” overdose was not statistically different from other decedents.

From this study: https://ndews.umd.edu/sites/ndews.umd.edu/files/ndews-hotspot-unintentional-fentanyl-overdoses-in-new-hampshire-final-09-11-17.pdf (Unintentional Fentanyl Overdoses in New Hampshire: An NDEWS HotSpot Analysis, Marcella H. Sorg, Ph.D., Jamie A. Wren, MPH Margaret Chase Smith Policy Center University of Maine, Kathleen Stewart, Ph.D., Yanjia Cao, Center for Geospatial Information Science University of Maryland)

Apparently according to Wikipedia; notable celebrity deaths from Fentanyl (either accidental or not):

Medical examiners concluded that musician Prince died on April 21, 2016, from an accidental fentanyl overdose.^[127] Fentanyl was among many substances identified in counterfeit pills recovered from his home, especially some that were mislabeled as Watson 385, a combination of hydrocodone and paracetamol.^[127][128] American rapper Lil Peep also died of an accidental fentanyl overdose on November 15, 2017.^[129][130] On January 19, 2018, the medical examiner-coroner for the county of Los Angeles said Tom Petty died from an accidental drug overdose as a result of mixing medications that included fentanyl, acetyl fentanyl and despropionyl fentanyl (among others). He was reportedly treating “many serious ailments” that included a broken hip.^[131] Additionally in 2018, American rapper Mac Miller died from an accidental overdose of fentanyl, cocaine and alcohol.^[132]

Or also note how dangerous fentanyl is, comparing heroin’s lethal dose and fentanyl’s lethal dose: