But instead of making them fast, it slows and calms them.
Alcohol makes you slow, dwarves go fast when drunk. Thus coffee and tea should make dwarves "drunk" by human terms.
I strongly disagree. I think dwarves slow down when drunk, not their bodies are from opposite land, but because they're alcoholics, and are miserable and vaguely hungover and generally distracted when sober.
Something I just thought of: I set SPEED_PERC to 50 in the caffeination syndrome, does that make them go 50% of their normal speed, or does it increase their speed by 50%
Something else I thought of, does the SPEED_ADD argument for CE_SPEED_CHANGE add the provided number to the dwarf's base speed, or does it change the base speed to that number? If the latter, people like Nil Eyeglazed might like to add a Hauler's Tea, with a syndrome that gives the drinker a nice regular speed, taking a lot of the timing guesswork out of certain devices.