this is quite a simple feature really, if you put a filled fluid container (e.g test tube, round bottomed flask, beaker) in your offhand you can hold right-click to drink it. and for the putting chemicals in people food/potions, put fluid container (e.g test tube, round bottomed flask, beaker) and food/potion of choice in crafting and it will empty contents of vials onto food. you will get vial back. effects of chemicals will now activate when eating/touching food

just a funny addition

it gets your friends to drink various funny liquids

~NthPhantom10