Pharma companies would already have a caffeine equivalent that would be only slightly different in structure so it would circumvent the law. It would then be sold at exorbitant prices and people would still pay even with the side effect of sometimes you eat someone’s face. Of course they would then sell you something else to stop the side effects. You would also have the caffeine purists who would start their own speak easies and organized crime. People “abiding by the law” would start calling the purist, plants, since that is where caffeine is coming from, while the synthetic caffeine users would be called zombies for the obvious face eating reasons. This whole thing would cause even greater divides between already split countries leading to all out war. WWIII plants vs zombies.

Michael Pollen wrote a audible book about how modern capitalism wouldn’t have been possible without the invention of the light bulb and the abundance of caffeinated beverages as it facilitated a 24 hour economy. Literally titled Caffeine: How Caffeine Created the Modern World.

So what would happen if the government illegalized caffeine? I’d say they’d be more likely to prohibit literally any other drug including alcohol and tobacco. But if I were to indulge this hypothetical scenario, I’d say other new stimulants without any legal status would be invented to replace caffeine.

It would be yet another failed policy pushed by the kind of idiots who like to ban things. Comics/Guns/Porn/Drugs etc.