If you are going to use this milk in a curry, stew, or smoothie, there is no need to add anything else. But if you are going to use it on cereal, or drink straight up, you may want to jazz it up with some sweetener:
Here are some suggestions:
Don't waste that leftover milk. Freeze it in ice cube trays, and them empty into containers or zip-lock freezer bags for use later in smoothies, soups, and other recipes.