Experiment: Coca Cola and Drain Cleaner

The (possible) patent has some good details ( link ) > The ink storage pipe includes an at least two-layer structure of an inner layer in contact with ink and a base layer, the base layer being formed of a paper base material and the inner layer being formed of a resin. The resin is preferably an acrylic resin, polystyrene, a fluorine resin, silicone or a mixture thereof. > In case of applying a resin film, the inner layer 4 has a thickness of typically 3 to 90 micrometre and preferably 5 to 60 micrometre. This honestly seems like the coke cans ( ▶ this video ). In any case, this should be easier to recycle than the cans.

Most metal food containers are coated with plastics like BPA. You can't trust "BPA free" labels because there are now analog compounds in use. For example this is what a dissolved coke can looks like.[1] 1. ▶ this video

Here's a demo with a Coca Cola can: ▶ this video Basically, you don't want any funny reactions with the metal.

They use a thin plastic liner to prevent reaction with the Aluminum. These will burn off when the Al is melted for recycling. Great video here: ▶ this video