Get a small glass or bowl, depending on what's available.
Pour apple cider vinegar until the cup or bowl is half full.
Next, put a drop of liquid dish soap in the vinegar. Literally a drop, and do not stir. You can use any brand dish soap.
You're all done with the mixture. Now find a good, out of the way place, preferably close to the problem area, and leave the cup there for a few hours. When you come back you will be AMAZED!