Water is Required but be Cautious: It can't be stated enough that the dragonfruit cactus will tolerate a period of dryness more than it will tolerate a period of excessive wetness! However, when the dragonfruit cactus is healthy and growing and producing lots of fruit (which are very rich in water content), the dragonfruit cactus requires a considerable amount of water! This may seem a contradiction, but remember that the dragonfruit cactus is a cactus after all - and that the fruits are very high in water content.
Too much water can cause rot and increase the chance of both fungi and bacteria attacking the dragonfruit cactus and kill the dragonfruit cactus directly - err on the side of caution. The best way to grow dragon fruit cactus plants always is to have this in mind!