When using vinegar to clean your Keurig coffee machine fill the Keurig with half water and the rest with vinegar.
Then run the Keurig through a normal cycle of making coffee but instead it will push the vinegar and water through the Keurig machine.
Then after that cycle finishes run some straight water through the Keurig machine again to remove the leftover vinegar and vinegar taste from the Keurig.
You don't want to have vinegar tasting coffee like I did one time when I failed to run the Keurig coffee machine through a second cycle to make sure it cleaned it out completely of the vinegar.
You can add just half straight vinegar as well without the water to really clean the Keurig but if you just need to clean the Keurig coffee machine just a little bit then using half water and half vinegar will work good.