You will need white vinegar and water. I use a measuring cup with a spout when I put water in my mini Keurig for coffee, or when I clean it. My aim just isn't that great!
This is the first time I'd done anything beyond brew vinegar to clean it. I decided to really clean it. So there will be a few elements you will need to take out.
These are the three elements. The smallest piece will be taken from the piece where you put your K-cup.
It looks like this when you pull it out of the machine. You will be pulling the bottom off it.
And then you will have this. I put my three pieces in soapy water in the sink, while I continued cleaning the parts you can't take out with a damp paper towel.
While this piece was out, the clear piece, I cleaned around the inside. You will see brown residue come off you didn't even realize was there.
I first brewed some water through it. Not sure why. Just thought it sounded good!
Then I ran three rounds (mug full) of vinegar through it. I was reading the Keurig instructions I'd kept in my files. But the amount they said to pour into the Keurig made mine really full and about to spill over. So I ran smaller amounts.
Then I ran 3-4 rounds of water through it. Then I turned it off and let it sit for awhile with the top up and without putting the three pieces back yet.
I thought this would help the vinegar dissipate. Then after an hour or so, I put it all back together.
I can't recall how often it said to do this, but every month or so I imagine would be wise. I run the vinegar through when my coffee mug isn't filling up with coffee as much as it usually does.