Tomatoes will sprawl all over and take up a lot of space if they are not staked or caged. Usually, a tomato cage is used to help keep the plant under control. The plants grow so large in a self-watering container that they may overrun a common tomato cage. I had a plant that was 8 feet tall a couple of years ago!
One solution is to build your own tomato cages. Keep in mind that the measurements given in the diagram probably won't be exactly right for your needs, and will need to be adjusted. If it is windy in your area, you will need to glue the PVC joints.