Some people feed it to their horses for its anti-arthritic and shiny coat effects. Barn owner?
I buy cider vinegar by the gallon when I’m making North Carolina-style barbeque sauce & smoking a lot of pork. It’s in both the BBQ and the mop sauce.
Seeing as how cider vinegar is Nature’s Wonder Cure For The Credulous, good for anything that ails ya, I’m not surprised people would be buying CV by the gallon to drink and bathe in. Here are just a few things it’ll heal:
ARTHRITIS
ASTHMA
BLOOD LOSS
COLITIS
COUGHS
DIARRHEA
DIZZINESS
EAR DISCHARGE
ECZEMA
EYES (TIRED AND SORE)
FATIGUE
FOOD POISONING
HAIR LOSS
HAYFEVER
HEADACHES
HEARING
HEARTBURN
HEMORRHAGES
HICCOUGHS (HICCUPS)
HIGH BLOOD PRESSURE
INSOMNIA
KIDNEYS AND BLADDER
MENSTRUATION
MUCOUS DISCHARGES
NAIL PROBLEMS
NERVOUSNESS
NOSE BLEED
NOSE - STUFFY
OBESITY
SHINGLES
SORE THROAT
TEETH
VARICOSE VEINS
WEIGHT GAIN
WEIGHT LOSS
EXTERNAL APPLICATIONS
FOR A BATH
ITCHY SCALP
I especially like the fact that it’s good for both weight loss and weight gain. That stuff really covers all the bases. 
Seemed like a douchebag, did he?
De-skunking a rather large dog.
Do they have barbecues in Alaska? That would be my vote – a big church picnic barbecue or other big event. Three gallons would make a lot of barbecue sauce, though – I’ve got a recipe that I have to cut down from a restaurant’s recipe and it only calls for a quart, I think.
Maybe he’s stocking up for the barbecue-free apocolypse.
Could be preserving air-dried meat or salami - often that involves soaking/washing in vinegar to retard the growth of pathogens.