Pour 1 liter of corn syrup, 5 liters of water, 2 to 3 tbsp. of red food coloring, 2 tbsp. of green liquid soap and 1 tbsp. of milk in a large pail or bucket.
Mix the ingredients with a long-handled metal spoon to avoid any staining of the spoon.
Add more red food coloring, by 1/2 tsp. amounts, if the color of the fake blood is not to your liking. Add more water, in 1/2 tsp. increments if the color is too dark.
Add more corn syrup, by the teaspoon, to thicken the mixture if desired. Add water, in 1 tsp. increments, to thin the mixture.
Store the fake blood mixture in a refrigerator. Keep and use for approximately two to three days if you added milk. If you didn't add milk, keep it four to six days in the refrigerator.