The watering schedule really varies with the plant size and the weather. On over 90 degree days even my plants in 25 gallon containers like to be watered two or three times per day. Earlier in the summer, when the plants are a bit smaller and the temperatures are in the 80's, the plants thrive with being watered daily or every other day. The plants very quickly show signs of water stress in hot weather, so pay close attention. If the plants gets stressed very much or very often, they will tend to get disease or suffer blossom end rot.
The best method that I've seen for tomatoes in containers makes use of the self watering containers. A friend of mine had great tomatoes, two plants per rectangular approx five gallon container. IMO that is by far the best route to take when trying to grow tomato plants in containers.