Water Wetter is two kinds of alcohol, with Sodium Molybdate, (anti-corrosive) Polysiloxane Polymer, (silicone) and Tolyltriazole (used sometimes to de-ice aircraft. Also an anti-corrosive.)
The alcohols are the main ingredients, they lower the surface tension of the water.
First Guess: You could get the same effect by dumping a few ounces of rubbing alcohol in the radiator, as long as there's anti-freeze to act as a corrosion inhibitor.
Second Guess: If you think you need this product, you have something wrong with your cooling system. Either it's under-sized for the heat load generated, there's a failure in the cooling system like a corroded radiator, or wrong water pump pulley ratio. Perhaps the engine is generating too much heat due to poor tune--lean air/fuel mix, retarded timing, etc.