It is difficult to get the symmetry right when painting any bottle. It is harder still with an old green glass Coke bottle. And it is very nearly impossible when you are looking down on the bottle from almost directly above. So, that is what I did.
As I was attending to liquids, I also practised a drop of water and a drop of wine.
And a drop of water …
… and a drop of wine. Looking at this now, I realise it resembles the Japanese flag in liquid form.