My water bottle is a leyden jar

At my desk at work, I keep an aluminum bottle for a ready source of water. Over time, I have coated the outside in green rubber bands, for no adequately explored reason.

Today, when emptying it into the stainless steel sink, I received a static shock. The circuit seemed to be made by the stream of water out of the bottle.

Today is a Monday. It has been sitting on my non-conducting desk for at least 2 days. The exposed surface is reasonably covered by insulators -- the rubber bands and the plastic screw-on top.

It's not quite a classic leyden jar, but pretty close.