When growing tomatoes you should water the tomatoes as often as a few times a week or whenever the top couple of inches of soil feel dry to the touch.
Newly transplanted tomato plants may require daily watering, until they are established.
Once the tomato plants are established then they often only need watering a couple of times a week, depending on the weather.
Young seedlings and transplants of tomato plants need more frequent watering than mature tomato plants.
Also hot and dry weather will also increase the frequency of watering and the need for water, and cooler and wetter weather will decrease the amount of water that the tomato plant will need.
If the tomatoes are planted in sandy soil, the tomato plants will need more frequent watering as sandy soil dries out faster than clay soil does.
If the tomato plants are in pots, they often require more frequent watering as tomato plants that are in pots often dry out faster.
You should always water the tomato plants, deeply and less frequently which encourages deep root growth.
And water the tomato plant as the base of the tomato plant and avoid getting the leaves of the tomato plant wet to prevent any fungal disease.
Water the tomato plants in the morning as it allows the soil to dry out during the day, and reduces the risk of disease.
You should also consider mulching around the tomato plants as the mulch can help retain moisture in the soil and use a moisture meter which can help you determine when the soil is dry enough to need more watering.