You can, Lewis. You have to change your mindset about these things.
However, I appreciate that it seems an awful lot to start to knock back from a standing start!
Why not build it up gradually? Start with 3 litres, perhaps. That's 1.5 large bottles. Honestly, you will find it easy to do once you get into it.
I don't know what your job is, but if you're at a desk, make sure that you always have a glass full of water in front of you.
And substitute one cup of tea/coffee/fizzy drink for water.
I can't manage without my coffee first thing in the morning, but instead of having a second one, I have water instead. That also means that the water I'm drinking is spread out across the day - I don't have to suddenly gulp down a litre at a time!