This is what chatGPT told me:

"The metaphorical imagery of the U.S. slurping up liquidity from other economies like a milkshake through a straw is the explanation commonly associated with the origin of the term."

Also here's an article from bitcoin magazine on the dollar milkshake theory, and the bitcoin extension: https://bitcoinmagazine.com/markets/weaponized-us-dollar-for-global-hegemony

Thank you for asking. I keep hearing about this, too, and it never quite rose to the level where I bothered to find out. Thanks for being on that wall :)

Here's a cleaner explanation than the bitcoinmagazine one linked below, with an interview from Brent Johnson, the guy who invented the term.

That, I don't know. Never thought about the why of the "milkshake" metaphor.

Sure it's not meaning this... 😛

"I Drink Your Milkshake is a phrase spoken by Daniel Plainview to Eli Sunday at the end of There Will Be Blood, directed by Paul Thomas Anderson. In the film, the phrase was intentionally used as a metaphor: sucking milkshake from someone else to demonstrate not only oil drainage from prized land but the harsh nature of how cruelty often trumps meekness"

In the movie he speak about drilling underneath someone else's land to steal the oil literally out from under them even though it's not his land. The movie is 2h 38m long and the scene is right at the very end. It's hilarious lol