How does soda get in the can and how do they get the top of the can on?
Cans are filled before the top is crimped on. The key engineering issue is that can walls are about 90 micrometers thick, so empty cans are light, weak, and easy to damage. The filling and sealing operations need to be extremely fast and precise. The filling head centers the can using gas pressure, purges the air, and lets the beverage flow down the sides of the can. The lid is placed on the can, then crimped in two operations. A seaming head engages the lid from above while a seaming roller to the side curls the edge of the lid around the edge of the can body. The head and roller spin the can in a complete circle to seal all the way around. Then a pressure roller with a different profile drives the two edges together under pressure to make a gas-tight seal. Filled cans usually have pressurized gas inside, which makes them stiff enough for easy handling.