Will drinking more water increase my milk supply?

This is a very common misconception. You would have to be very very dehydrated for it to affect your supply.
So, drinking more water will not increase your supply. Back to basics… 3 things increase your supply; Emptying your breasts, emptying your breast often and stimulation. Side note: water pills as well with allergy pills will lower your supply because they’re meant to dry things up in your body. They can be helpful if you are wanting to quit breastfeeding and want to help to dry up your supply.