Root Beer
This is kind of an assassination tool, maybe? Although it doesn’t exactly kill people. It instead changes their personality, positive and negative traits, and skill sets. So, it’s pretty nasty stuff: you may not die after drinking it, but after whoever gives Root Beer to you gets done with you you won’t be the same person in any real, meaningful sense, either. One of many reasons why it’s rather thoroughly banned, except in the most advanced Galactic cultures, under the most rigorous bioethical guidelines.