Soft drinks are a way to kill the time, an ice breaker in a conversation and much more.. sure! But until and unless you are at an expensive restaurant what you drink from the bottle or tin might not be just coke. Don't panic. They aren't trying to kill you and steal your money.
What I'm trying to say is that there is a high chance of accumulation of dust on the cans or rust on the tins that you will not see right away. Shopkeepers generally don't wipe their tins before refrigerating them. You might swallow a bit of dust on the top along with the drink. You can use a tissue and wipe it off before you start sipping away.
Be extremely cautious with the glass bottles though. The crowns of the bottles are prone to get rusted and guess where it sticks. That's right! Right where you put your lips to the bottle. Always make sure that you wipe the rim with a tissue before enjoying your Coke cold.
Or go for a pet bottle and save yourself some rust, dust and moolah, if you can recycle the bottles of course.