Depends on plant size, and how much the plant us drinking. Along with temperature, and air flow, and soil composition.
But generally 20% of Liters of soil for peat perlite, and vermiculite Medium base.
At the height of budding from a plant using a good amount of water, at 27.7c, Id use 27.7 liters of water. Thats in 75.7 liters of soil/Promix BX which is a fairly light medium.This would usually last 3.5-4 days between waterings in 75.7 liters of soil, under 100w HPS/Hortilux, and a large fan, or 2-3.
This is only a generalization using a Super Silver Haze strain/pick as an example. Many strains would use less, but few would use more than this particular plant I picked out of 250.