It is an old technique that goes back at least decades. I remember my dad did it in the 1960s with large vegetable cans he got from the lunchroom ladies at our local elementary school. Lots of people in Texas do it with clay pots or with plastic buckets, milk jugs, etc. with small holes drilled in the bottom so water can slowly drain down into the soil. In Texas, it often is referred to as the Texas Pot Method, a name popularized by the late, great horticultural legend, Dr. Sam Cotner. I've linked an article below that explains how he used the Texas Pot Method not just to water tomatoes but to fertilize them as well. Keep in mind that the method as described is how it was utilized in the sandy soils of east Texas and you may need to adjust how many times you fill the container with water and how often you do it depending on your soil You could start with his recommendations and then adjust them to meet your plants needs.

Here in the real world where we all live and garden, you really cannot water on a schedule because some months you might have 4 or 6 or 8" of rain and other months you might have an inch or less. The kind of soil you have as well as how quickly it drains (or doesn't drain, as the case may be) plays a role in how often you water. Thus, no one can tell you how often to water. You need to keep your soil around your tomato plants evenly moist because having the soil swing back and forth from too wet to to dry can contribute to various problems, including blossom end rot. If your soil is nice and loose you can just stick your finger (or a trowel or a dowel or stake) down into the soil to see how moist the soil feels. If your soil is dense and compacted, you can hammer a stake or dowel into the ground and leave it there. When you want to check the soil, just pull the stake out and do your best to determine how wet the end of the stake is. If it is bone dry then the soil down at that depth likely is bone dry as well. Or, if you like gadgets, get a moisture meter and stick the probe into the soil to check your moisture level.

Realistically speaking, in most of OK in most soils, tomato plants need at least 1" of water per week for good growth and in the hotter summer weather they need at least 2" per week. With soil that drains extra fast, they may need more than that if it is really hot and the plants are transpiring lots of moisture via their leaves. You have to study your soil and learn how well it holds moisture in the root zone of the plants and make your watering decisions based on that.

Hope this helps,

Dawn

Here is a link that might be useful: The Texas Pot Method of Watering/Fertilizing

My Earthbox tomatoes water themselves but, when I have plants in the ground, I only water when they begin to look a bit droopy.