Cheap vodka, and DISTILLED water, not water from the tap unless you boil it first to remove any impurities. I use the water from my dehumidifier, which is the same as distilled water. I make mine with just a few drops of lavender oil in it, have had it in a gallon jug for a year and no problems with "gunk" in it.
Sorry, Learning2Quilt, I didn't see your post before I typed mine.