[gusmd]

You are neglecting the fact that a soda can is pressurized once, depressurized when opened for consumption, and then wasted.

An aircraft fuselage needs to withstand THOUSANDS of cycles of pressurization / depressurization during its service life, which is usually much more critical then the static pressure load, due to metal fatigue. This is why aircraft service life is given in flights (which corresponds to one pressurization cycle) and not in flight hours or miles or whatever. This is also why aircraft used on longer routes tend to last for more years (longer flights = fewer pressurization cycles).

edit: If anyone wants a reference, here goes one http://www.airspacemag.com/need-to-know/what-determines-an-a...

edit2: Additionally, consider checking my response to another comment. The diameter of the fuselage is so much bigger than the soda can that the actual stress on the walls are roughly only 1.5x bigger on the soda cans.