Over time, mineral deposits can build up in your Keurig coffee maker, affecting the taste of your coffee and reducing the machine's performance. To clean your Keurig water tank with vinegar, start by filling the tank with a 50/50 mixture of water and white vinegar. Then, run the machine without coffee grounds for a few minutes to allow the mixture to work through the system. Finally, flush the machine several times with fresh water to remove any lingering vinegar taste.