Blown head gasket temporary fix

There are a number of snake oil treatments out there. Some people have had moderate to rare luck with some of them. I wouldn't recommend it. If you do you have to follow the instructions exactly. The filling it with water part is something that is done before the stuff is put in and you have to flush out all the coolant first because the chemicals won't work with any coolant. After the process is all finished, then you have to refill it with coolant. It could do more harm than good though.

They also sell types that dont require removing antifreeze. Retorque the head bolts is also something to consider.

Just follow the instructions on the bottle. If it says get rid of the anti freeze first, then get rid of ALL of the antifeeze. Leave nothing behind. I wouldn't mess with the head bolts. Most of them are using torque to yield bolts and all you can do is snap them off and then your problem gets much worse.