Here's what I'm doing to help keep the hanging basket Tomatoes from completely drying out when it's super hot.
I replaced the caps with liquid soap caps that fit and cut off the flip lid. They are on their sides and the water doesn't pour out. The idea is that when it's super hot, the expanding heated air forces the water to drip out. Drip by drip. So it's not the same as automated watering -- you still have to water them once a day, but I can get away with not watering them again later in the day, and so far they have survived until next morning's watering.