Today I've just done a front brake service with fitting a new master cylinder kit because the old one was feeling a bit notchy. I borrowed my wife's water container for which she uses for topping up the iron with. (Don't tell her Mike)
It's perfect for filling up the reservoir with. It doesn't spill fluid because of the little pouring spout.
Don't worry everybody. I wet into town later and bought her a new one. I don't want my knickers smelling of DOT 4.
Bit of advice. Buy a good bed and a good pair of shoes, because if you aren't in one you'll be in the other.