Substitute to milk in coffee? I'm looking for a substitute to milk in the coffee... something that will have the same effect on the coffee (tone down the bitterness of a coffee cup) put that wont turn bad after two weeks.

Here's the situation... I do like to take a good coffee when I'm a little sleepy on the job... that happens, well, maybe once a week.

But if I buy a 1L carton of milk, it will have the time to turn bad before I'm at the halfway point. 

So is there a product that I could use to substitute the milk in my coffee that wont turn bad?
For coffee, there is milk in 10-ml portions. It is UHT, so it doesn't start spoiling until you open it, and you only open one of them per coffee. Alternatively, use powdered milk.