It goes back pretty far. That guy in To Kill A Mockingbird was always drinking from a bottle in a bag and they assumed it was alcohol. It ended up being Coke.
Yeah! I want to know this too.
I think he was specifically what is now called the Wesleyan Church. Same basic theology (Arminianism, etc.) but more evangelical. So both them and the United Methodist Church are under the Methodist/Wesleyan umbrella. But IME Methodist implies UMC in the US.
Gonna check their poop for dye? I’ll post it, although I don’t know if it’s the best method in your case, but I hope it helps.
Get 2x however many water bottles you want to fill with vodka or whatever. They should be identical, and have the “taller” lids like Crystal Geyser as the <1cm ones are harder. The following part assumes two paired bottles #1 and #2, repeat the steps if you want more. #1 is a sacrifice.
Bottle 1: cut the top off (clear plastic) above the water line. Keep the severed top, drink the water or pour it out if you hate the environment. Do not unscrew. You don’t need the body of the bottle anymore.
Bottle 2: remove the cap and drink. Cut off the plastic ring that sealed the top on, discard both parts of the cap. Drink.
Now you have an intact bottle with no cap, and the sealed top with only a little of the body. Boil water in a shallow pan and toss the top in. After awhile, work at it with needlenose pliers or similar and remove the opaque top without breaking the seal. Fill the intact bottle with liquid of choice, making sure to match the level of a regular bottle. Carefully screw on the intact cap.
Now you’ll feel vaguely like a lush at festivals but at least you’re not paying $9/flat Heineken, and are still probably in the bottom quartile for intoxicatedness among festival goers. Important: mark the bottle subtly so that you don’t use vodka as eyewash or something. When shaken, vodka does bubble differently but I’ve never know the security to check.
Nope, going to look for whose mouth is a weird color. 
When I was a younger man in a college town and I used to occasionally visit a local liquor store for a 40 oz. bottle of malt liquor (Mickey’s, O.E., etc.), the clerk would almost always ask if I wanted “a sleeve,” which was a brown paper bag that fit tightly around the bottle. It provided a bit of insulation (keeping your hand a little warmer) and kept the bottle from being slick and hard to handle, so I’d always accept. The side benefit of feeling like a gangsta rapper from a circa-1993 rap video was a bonus.
ISTR there was a scene in To Kill a Mockingbird where the town drunk gave Scout a sip from the bottle he had in a paper bag, and she was amazed to realize that it was root beer. The “drunk” felt he had an image to maintain in town.