metallic water container is not a very strict definition so it's hard to tell what exactly you mean :)

In order to place something in orbit you need to accelerate it horizontally to about 7.5km/s. The issue of using a "cannon" is that such device applies force only for a very short time when object is moving through the barrel. This means the acceleration has to be extremely high and as a result the applied force has to be very high as well. So your "container" has to be able to withstand compressive stress.

There is another, more problematic issue - once you leave the barrel you hit the atmosphere, and hitting atmosphere when moving at such velocity will cause atmospheric compression and heating (just like when spacecraft come back from orbit) slowing you down. So the container has to be able to withstand the heating, and the cannon has to eject the payload much faster than orbital velocity.

If you can get material like that, then you could launch it in such a way :) However, a more "practical" version of this idea would be to build a very long vacuum tunnel somewhere in high mountains. Long tunnel means you accelerate over longer distance, and if you place the nozzle of the cannon very high (let's say 8km) you hit much thinner atmosphere.