I would not necessarily add coffee sticks as a negative keywords, but I also would not target it either. I suspect that having it as a targeted keyword will result in a low QS, perhaps high bounce rates (no matter the landing page design and copy), low CTR and perhaps a relatively high cost per conversion/acquisition.
I suppose if you are looking for extra conversions you could target coffee sticks after all and have a dedicated landing page designed to either convince them that ground coffee is a better way to experience coffee drinks, etc. than coffee sticks. If this campaign does not yield significant conversions then scrap it as it could be a money loser at worst, or low ROI at best compared to your other campaigns.
In short, I think it best to target those who are actively looking for coffee grounds (keywords like overnight shipping, or quality ground arabica, etc. + your keyword) or even those who are shopping around for best prices, etc.
Targeting those wanting coffee sticks, K-cups, canned coffee drinks, etc. is possible but they may only want non-ground coffee so you will have to get a little creative to capture conversions from the non-ground coffee shoppers as there may be a few that can convert. This maybe at a higher cost per conversion.
Just my 2-cents.