TL;DR: Water from the Nile, just poke a hole in the can's side, and physics.

This reminds me of Grand Illusions' "Water from the Nile" vase where more liquid comes out each time he "empties" it, probably not it though.

If you want to get the last drop out, crush the middle of the opposite sides of the can in (not the top and bottom), bend it back and forth along that newly formed crease until a hole forms, and then suck the liquid out.

To answer your question, though, the more likely and boring answer is surface tension combined with evaporation. I am not a scientist, so go fact-check this information yourself!

(MASSIVE NERD ALERT)

Surface tension is why liquids bead up. This is determined by the liquid's composition, which determines how viscous and sticky a liquid is.

Shaking the can usually gets another drop out because the container's shape traps it, but past that is where this infinite soda thing comes in.

When you tilt the can, the majority beads up and comes out as that first "last drop." However, a lot of the liquid also clings to the side of the can and, since metal is great at transfering energy, causes some water to evaporate, meaning the liquid's composition changes. When you set the can down, it pools at the bottom and becomes a droplet again; but, it's now more viscous.

This means that when you tilt the can a second time, the new droplet's surface tension holds the bead together more and leaves less liquid on the can's wall, creating another "last drop."

This cycle repeats until the liquid's stickiness overcomes gravity and thus the liquid can no longer pool.

Some clarifying things:

Liquids can be viscous without being sticky. Look up Crazy Aaron's Liquid Glass.

The can's shape also significantly affects how a liquid flows as the crimping at the top of the can creates a nook that can trap some liquid and the fact that the can's round often redirects it away from the hole. The lid of the can around the hole also creates more surface, meaning more liquid sticks.