As soon as a put antifreeze coolant into the.

If it is leaking that fast, there has to be a puddle under the vehicle where it is leaking. If there isn't, get a pump to pressure test the system. Most parts stores will lend them to you. Pressurize the system to help locate where the leak is.

I had one other thought. If you don't see any coolant leaking, check the engine oil to see if the coolant is getting into the engine.