2 Litres of Water Each Day

It's recommended we drink 2 litres of water / fluids per day. It doesn't seem like a lot, but the discipline of it is something I'm finding really difficult.

When I was at home last week, I filled up a bottle each day and used to gauge my water intake. Even this wasn't as easy as it sounds. For example, for a cup of tea (caffeine free), I pour out a cup full of water, empty this down the drain, then re-fill the cup from the kettle.

Now I'm back at work, the system has gone to pot and I have no idea how much I'm drinking.

Does anyone have a solution for this?