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Trick question: They're actually drinking a secret Monster product, and collectors are desperate to get their hands on it.

How Do Warped Tour Bands Chug Energy Drinks In The Sun All Day Long?

If you check out the artists on this summer's Warped Tour, you might notice them drinking a LOT of Monster Energy Drink -- like, more caffeine than most of us could handle in 90-degree heat -- and perhaps even bathing in it:

But you can't always believe your eyes, because Reddit user SmackyRichardson noticed a slight difference in the bands' Monster cans versus the ones distributed to fans:

Imgur: SmackyRichardson

It's called Monster Tour Water, and it's only available backstage -- a Monster employee tells us "it's never been sold anywhere" -- thus making it a highly sought-after collector's item. (Right now it's going for $13.99 on eBay.) But SmackyRichardson feels it's a health hazard:

"Kind of dangerous in a way, as anyone who was actually chugging that many Monsters in 100 degree heat would more than likely kick the bucket. Warped tour is full of impressionable tweens who want to look as cool as their idols onstage."

Not everybody agreed with her theory, and this is actually nothing new -- Warped Tour has had branded water for at least a decade:

Kyles Monster Energy Collection

As one Reddit user explained, it's not worth getting THAT excited about:

"I work for Monster and we drink tour water at most events we do. If people do notice, they are so intrigued and want one. Its just water in a can, man..."

But if you don't read the fine print, it may come as a shock:

"I remember discovering that accidentally when I worked my first Warped Tour. Popped one open backstage and went to enjoy a sweet sip... Even when the resulting taste is not a strong one, it's always shocking when you expect one flavor and something very different hits your mouth. Spit it out and freaked out, then read the can."

Some people are calling it a marketing conspiracy:

But the fans and bands seem pretty cool with it:

Old-school political punks might be turned off by the caffeinated sponsorship, but hey, at least H20 is healthier than most of the stuff Sid Vicious put into his body, right?