As a new member and this being my first post I've been reading the forum on growing tomatoes upside down and the different comments on them and the various results.
I too have and am growing tomatoes upside down and have a couple of comments on the reason for some of the results I see on the forum.
First: Growing tomatoes in general is and can sometimes be a hit and miss proposition. but when growing them in and upside down container can add yet other challenge to it as well. Not as far as the upside down part because the tomato doesn't care whether is root system is above it leaves or below it as long as it gets the proper nutrients. As you all know tomatoes are mostly water and it takes a lot of it to grow them, especially in a container that it exposing its root system to the heat of the sun in mid-summer. Watering has to be consistent and with the proper amount. If not, blossom end rot will occur.
Second: Since most tomatoes (verities such as Heatwave will) will not set fruit once the temperature reaches above 95. When growing them in a Clear 3 liter bottle this is creating a greenhouse effect and will increase the root zone temperature substantially. Thus this will cut down on the production and will result in less harvest as some have complained about on this forum. One solution to reduce that root zone temperature is to wrap the bottle in a foil reflection insulation. Also for a few bucks at your local big box lumber store you can put in a drip irrigation system which provides constant water and reduces the labor intense chore of watering or to remember to water. This will reduce or eliminate blossom end rot and produce more fruit.
Third: And final thing I recommend is to prune them and only keep about 2 main stalks if they are determinate and to keep all the suckers pruned off if they are indeterminate varieties; this will cause the tomato to put more energy into producing tomato and less energy into the foliage. and to sustain that energy they need to be fed or fertilized at least every three weeks or so. Good luck.