From IvanWiki

General

Cans are used to store food so as they do not rot at all, regardless of type. This is a very good way to preserve food.

You can dip (!) potions and liquids into cans. This will stop them from shattering due to explosions. Cans have about 1/2 the capacity of glass bottles, so it is also useful for preserving healing liquid when you do not need the full dosage early in the game.