Growing tomatoes upside down seems to be one of the more inventive methods of container gardening I have seen out there. This type of Container tomato growing can actually yield good crops, and when done correctly, they have even been seen to improve condition and yield over conventionally grown plants.
The increase in productivity seems to be due to an increase in circulation of air around the stem, leaves & flowers when hanging in the air. There is more uptake of nutrients and water due to feeding the bottom of the roots and less propensity toward disease as they avoid
contact with the garden soil.
I think my favourite part of growing tomatoes upside down has to be not having to stake them ! When taking advantage of gravity, you can simply let the plant grow downwards, take off the laterals as normal and the weight of the plant is distributed evenly through all the branches.
It is possible to grow many types of tomatoes upside down, but the best varieties will be the dwarfing type with high yields or shrub types. Indeterminate types can be used but be prepared to reinforce the container due to weight of the plant. Another method to halt the downward growth is by pruning out the growing tip allowing the plant to grow more shoots laterally.
It is best to keep all types of upside down tomatoes pruned to a more manageable size and
these plants will be more healthy, bear better sized fruits and actually ripen faster.
A few varieties that are more suitable for being grown upside down are Early Girl, Sun Gold, Bush Celebrity, and Pink Ping Pong.
Here are the 6 easy steps to building a planter for growing tomatoes upside down:

bottom inside. Remove the plant from its container and carefully stick the plant through drilled hole so your tomato sticking out from the bottom of the bucket (upside down). Hold the plant in place so that there is about 3cm (1inch) of stem sticking out of the bottom. 

And there you go !! a quick and economical tomato plant grown upside down. Like all container vegetables, make sure to water and fertilise it in regular intervals.
Mulching on the top of the planter is also an excellent idea as it prevents evaporation and water loss. Conifer or composting mulch is the most popular, but you can also cut up a black rubbish bag and us it to cover the opening of the bucket.
Tie the bag around the bucket with a piece of string, and cut an opening on the bag where water and fertilizers can enter. Although, I simply cut a hole in the top of the lid which allows cover and air flow. You could also have auto watering containers that slowly drip into the plant.
While my example may seem a little primitive, it was also free and will yeild a good crop !