What rainbow said. 5gal is like MINIMUM. At that, you'll be watering probably twice a day once fruiting begins. Something like 15" cubed would be better.
Also, the support should be sturdy and need to support both the container AND the plant, or the whole thing will topple over especially when the soil is dry or when wind is strong. Say something like 4 1" bamboo or 2" wooden stakes 12"-18" in the ground surrounding the container -- so at least 6', 7' would be better.... Some people drive the stakes THROUGH the bottom of the container.
If the containers are on a solid surface, secure the stakes in the container to a solid structure like fence post. Another way is to have some kind of overhead structure (veranda/balcony? swingset? arbor?) from which you can hang strings that you can wrap the vines around as they grow.
...take a look at the tomato support sticky at the top of this forum for some ideas that you could adapt for container growing.
What I like to do is use a slender bamboo or straight branch to support smaller seedlings initially so they don't fall over, then build or set a sturdier support around the plants as they grow. I try to minimize foliage-soil contact to avoid soil borne diseases.
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