You will want a good quantity of bubble solution. I went to Wal-Mart and they had a six-pack of large bubble bottles. Each has a wand in it.
Fill your container so that the bubbles cover the end of the wand every time the wand is dipped down by the servo. If you try the machine out and the servo is not moving the wand correctly you can either take the servo horn off and twist it or change the angles in the code to the two locations you need.
Consider using this project outside. the bubble solution may spill and the bubbles popping will make things wet and soapy.