It may be less about watering and more about feeding. Tomatoes love high nitrogen soil with good drainage, they will send roots deep to find the water.

Next season, dig a hole 2 feet deep and 1.5 feet wide for each plant. Place a sturdy trash bag in the hole. Fill the hole 1/3 of the way with gravel, 1/3 of the way with sand and 1/3 of the way with a mix of topsoil and organic compost. Water until the water stays on the surface. Wait until the topsoil dries out (about a week) then plant the tomatoes and add 1 gallon of water. Once a week after that add 1/2 gallon of water.

This method creates an artificial water table that keeps the plants roots fed and a nutrient layer that feeds the plant. Once Every 4 weeks during the growing season add 1/4 inch of fresh compost around the edges of the hole, keeping it about 6 inches from the stem to avoid fertilizer burn.

When the tomatoes grow, there will be branches with flowers and branches without flowers. Cut off about 1/2 - 2/3 of the branches without flowers at the main stem, this sends more water and nutrients to the fruit.