When you drink coffee w/ half & half no substitute will do, not even whole milk. On the other hand seeing your milk leak into the cooler water is icky and just a bad start to a morning with so much potential. I have tried pouring small amounts of half & half into a plastic container and so far it has leaked every time. This little pint size container with the screw lid is the best way to go as far as I'm concerned.
They don't leak ! They do cost a bit more though.
About a month prior to my camping extravaganza I will start looking for them when I do my shopping. Many times they are on sale and the expiration date is far enough out that it is safe to buy in advance.