Not sure if anyone still order 'take-away' kopi in such cans, but I'm sure we remember these 'cans' kopi from earlier days. Those were the days when styrofoam cups were uncommon, and coffeeshops re-used the milk can to make kopi (it also make use of the last bits of milk in the cans!). Somehow coffee served in such cans taste better than those in styrofoam cups.
I ordered one such kopi today, and the coffeeshop auntie actually smiled when i said 'kopi - kong' (kong is hokkien for can). Anyway, the design is quite ingenious because the whole can is held intact by the slight dent at the can opening, such that the 'cover' is locked safely. To open the can of coffee, one only needs to press the side of the can slightly, and the 'cover' would spring up.
So next time try a 'can' of such coffee, and see if you like it.
Afternote: This post was 'yesterday'ed'!