In my car, coolant dries up fast and after i drive around 400 kms, again I have to feel up at least less than a half litre. Why it is? No leakage.
You could have a head gasket leak into your cylinders
If you do have that issue you would not see any coolant leaking from the motor. It would be going into your combustion chamber where the air and fuel are ignited thereby driving your piston down.
You would troubleshoot this with a leakdown tester or a compression tester.
Leakdown Tester Instructions
This is a similar post that illustrates blown head gasket troubleshooting. The difference in your case, if you have a blown head gasket would be that you are leaking coolant into your combustion chamber instead of into your oil.
Here is an article on howto perform a compression test.
If you have no coolant leak and you are losing coolant there is a good chance that it's leaking into your combustion chamber.
Hope this helps, cheers!