Waste is pretty easy. This bag:
But I can find quick oats in bulk. So let's look at cost, in ascending order, starting with the cheapest:
So bulk is more expensive than your big container of store-brand quick oats, but is still cheaper than the packets.
And we came up just shy of half a cup. But that doesn't mean anything. Not all instant oatmeal packets are the same and you're just gonna eyeball the water amount at your desk anyway.
To make it portable, you could use an old spreadable butter container. Or you could buy some backpack insurance by using a rubber band or a container with lockable sides.
Make it like you would instant and you've got a quick, Zero Waste breakfast.
*The nutritional makeup is the same, but instant and quick oats have higher glycemic indexes since they are more processed than rolled or steel-cut oats. So they get in your system faster but don't keep you feeling full as long. As a bonus, the quick oats you find in bulk have a slightly lower GI than instant but cook just as fast.