If your Keurig coffee tastes burnt it is most likely caused by a build-up of oils inside your coffee maker. If you don't keep on top of regularly cleaning your Keurig coffee machine, residue from previous coffees can build up. This will lead to bitter and burnt flavors making their way into every coffee you make. To fix this problem you need to clean your Keurig coffee maker thoroughly and frequently. Using a vinegar solution to flush the system of any nasty build-ups is ideal. Just remember to run a lot of water through it afterward to avoid swapping burnt coffee for vinegary-tasting coffee. After cleaning, your coffee should return to its normal, delicious flavor.