If you don't care about the car and have no long term plans for it, then there are plenty of different stop leak products that might, or might not work.
But, these products work by solidifying in the cooling system where is a leak to air, or a change in pressure.
They can often block critical passages in the engine and cause over heating problems in the future.
Can you see where the leak is?
Usually they are not that hard to fix, and long term it is always the better solution.