Yeah, I got it working. For some bizarre reason, it only works if I place the [MATERIAL_REACTION_PRODUCT:] thing before the actual drink definition, but now I can have things like this:
[PLANT:BEAN_ELF_KILL]
[NAME:laughing bean][NAME_PLURAL:laughing beans][ADJ:laughing bean]
[USE_MATERIAL_TEMPLATE:STRUCTURAL:STRUCTURAL_PLANT_TEMPLATE]
[MATERIAL_VALUE:1]
[EDIBLE_COOKED]
[EDIBLE_VERMIN]
[BASIC_MAT:LOCAL_PLANT_MAT:STRUCTURAL]
[PICKED_TILE:13][PICKED_COLOR:2:0:0]
[GROWDUR:600][VALUE:1][MATERIAL_REACTION_PRODUCT:BOOZE_MAT:LOCAL_PLANT_MAT:DRINK]
[USE_MATERIAL_TEMPLATE:DRINK:PLANT_ALCOHOL_TEMPLATE]
[STATE_NAME_ADJ:ALL_SOLID:frozen joy brew]
[STATE_NAME_ADJ:LIQUID:joy brew]
[STATE_NAME_ADJ:GAS:boiling joy brew]
[MATERIAL_VALUE:3]
[DISPLAY_COLOR:3:0:1]
[EDIBLE_RAW]
[EDIBLE_COOKED]
[SYNDROME]
[SYN_NAME:elfblight]
[SYN_INGESTED]
[SYN_INHALED]
[SYN_INJECTED]
[SYN_CONTACT]
[SYN_AFFECTED_CREATURE:ELF:ALL]
[CE_NECROSIS:SEV:300:PROB:100:START:1:PEAK:40:END:50]
[CE_PARALYSIS:SEV:300:PROB:100:START:3:PEAK:40:END:50]
[SYNDROME]
[SYN_NAME:joy rush]
[SYN_INGESTED]
[SYN_INHALED]
[SYN_INJECTED]
[SYN_CONTACT]
[SYN_IMMUNE_CREATURE:ELF:ALL]
[CE_PHYS_ATT_CHANGE:AGILITY:200:0:START:0:END:30]
[CE_PHYS_ATT_CHANGE:STRENGTH:200:0:START:0:END:30]
[CE_ADD_TAG:NOEXERT:NOPAIN:NOSTUN:NONAUSEA:PARALYZEIMMUNE:START:0:END:30]
[PREFIX:NONE]
[DRINK:LOCAL_PLANT_MAT:DRINK]
[USE_MATERIAL_TEMPLATE:MILL:PLANT_POWDER_TEMPLATE]
[STATE_NAME_ADJ:ALL_SOLID:happy flour]
[STATE_COLOR:ALL_SOLID:GREEN]
[DISPLAY_COLOR:2:0:0]
[MATERIAL_VALUE:15]
[EDIBLE_VERMIN]
[EDIBLE_COOKED]
[PREFIX:NONE]
[MILL:LOCAL_PLANT_MAT:MILL]
[USE_MATERIAL_TEMPLATE:SEED:SEED_TEMPLATE]
[MATERIAL_VALUE:1]
[EDIBLE_VERMIN]
[EDIBLE_COOKED]
[SEED:laughing bean seed:laughing bean seeds:1:0:1:LOCAL_PLANT_MAT:SEED]
[SUMMER][AUTUMN][WINTER]
[FREQUENCY:10]
[CLUSTERSIZE:3]
[PREFSTRING:poisons]
[WET][DRY]
[BIOME:SUBTERRANEAN_WATER]
[UNDERGROUND_DEPTH:3:3]
[SHRUB_TILE:58]
[DEAD_SHRUB_TILE:58]
[SHRUB_COLOR:2:0:1]
[DEAD_SHRUB_COLOR:0:0:1]
With this reaction:
[REACTION:BREW_TEST]
[NAME:Brew drink]
[ADVENTURE_MODE_ENABLED]
[REAGENT:container:1:FLASK:NONE:NONE:NONE]
[EMPTY]
[NOT_IMPROVED]
[PRESERVE_REAGENT]
[REAGENT:plant:1:PLANT:NONE:NONE:NONE][HAS_MATERIAL_REACTION_PRODUCT:BOOZE_MAT]
[PRODUCT:100:3:DRINK:NONE:GET_MATERIAL_FROM_REAGENT:plant:BOOZE_MAT]
[PRODUCT_TO_CONTAINER:container]
[SKILL:BREWING]
Now I can make a special drink that kills elves, but provides massive boosts to anything else.