Before you begin, add 14 ounces of water to your slow cooker. Make a note of where the water line reaches (I use a ruler). This is where the milk level will be once your sweetened condensed milk is ready. Discard the water before setting up the milk in your slow cooker.

To make the sweetened condensed milk, add the milk & syrup to your slow cooker. Set it to HIGH, and let the milk cook down, uncovered, 8 to 10 hours, until it reaches the level you made note of with the water.

Once the sweetened condensed milk is ready, let it cool, and transfer to a glass jar. Store in the fridge until the sell by date of the milk you used to make it.