How much water do plants need to grow?

That depends on what kind of plant it is. Some plants, such as cactus, do not need much water. Other kinds of plants need more. So you would have to ask about a specific plant in order to get a specific answer.
It really depends on the plant. Some plants need more water than others, such as a cactus and a bean ,the bean needs more water than the cactus because the cactus stores water and beans don't.