I don't think my DS drinks anywhere 1L a day... I always have a sippy cup with water around and encourage him to have a sip when I think it's been awhile without one and he also helps himself sometimes too. But I usually only refill once a day... I do give him water in a cup with meals though, which has a bit of a novelty value and increases the amount of fluid he takes in...

Some people just have smelly urine (my DH especially, it stinks and he drinks heaps of water). I think all you can do is encourage him to drink as much as you can, but ultimately it's out of your control, they'll drink what they drink.

But a couple ideas to make it a little more interesting would be:
• get him one of those cool twisty/twirly straws to use
• put a drop of food colouring in his water - let him choose the colour and then he only gets a different colour when it's all gone
• ice cubes in the water for the novelty - you could even try putting food colour in these instead of the water.

HTH