My bottle of choice was a 3 liter water bottle- partly because it was 3 liters instead of 2 and partly because I didn't want to drink 2 liters of soda before embarking on my project. I painted it, which is important so that any roots don't get burnt by the sun coming through clear plastic. Then I cut off the bottom.
From the very first day, the leaves started to slowly turn upwards towards the sun (ever wonder why this happens? It is so interesting... basically, the leaves need to maximize the sun exposure, and the way they do it is that the plant cells that are in the shade start to elongate relative to the cells on the sunny side, and having the longer cells concentrated on one side causes the plant to bend. pretty clever, right?)
Not only are the leaves now completely turned upwards, the upside down plant is also grown a much larger percentage of new leaves close to the base of the plant than the right side up plant is (which makes sense). It hasn't managed to produce any fruit, but maybe that makes sense given how much extra work it has to do! Either way, I'm rooting for it!