I would imagine that's even more attractive to them in the old days, when they dealt in coins and bills. A modern vending machine probably mostly gets credit card transactions, which are traceable.
These days, it's almost trivial to launder via wash trades with the proliferation of online services with effectively zero marginal costs. e.g., setting up a freelancer account and a separate business account on some platform like Upwork and then hiring yourself. So I'd be surprised to see anyone laundering via sale of goods unless they are deeply incompetent or it's an opportunistic scheme of some sort (i.e., they are exploiting a unique opportunity that pops up).
like an MS Paint drawing of a monkey, but on the blockchain.
You are right about needing to buy cans that you can then pretend to have sold. Unless of course you order from a supplier who is willing to write an invoice for a higher number of cans than he has sold you. I assume a more competent group would also own the supplier (though not, perhaps, on paper).
more often this is done not in soda which has a street price that you can't get absurb values on. Better to sell a custom leather purse which can sell for a lot but you can make a junk one for almost nothing.
"If you buy this $600 cable and include the code CC in the order we will make sure to ship it with some white powdery desiccant packages included to protect the cable"
I mean not all of it, there are enough people with more money than brains to keep the legitimate(hah, right. I guess as legitimate as these sort of companies get) companies around. But sometimes you see a product priced so outrageous, you think there has to be something else going on.