There's a 24mm drain plug in the bottom and a 17mm fill plug in the front.
Probably the easiest way to fill for a DIYer without air power is to drill
a hole in the bottle lid and insert a hose. (Make the hole just a little
smaller than the hose so it will hold the hose in place when you force it
through). Pull the air intake ductwork from the front of the car and fill
from above using the hose.