I'm at 1.2L so far (but it's only 9am here). I'm going to try to get to your 4L - you've set a challenge for me.

I drink a golden circle (australian brand) diet soft drink sweetened with splenda. The problem is, it also has a touch of real fruit juice in it. Some flavours have 2-3 carbs. If I have 2 cans a day, that's carbs that could be better spent on some veges or something a little more nutritious. So, I'll try to give it up for the week!

Cheers,
Wabi