If you prepare recipes which require only egg whites or egg yolks, then consider freezing them already separated.
So, besides freezing ice and eggs, there are several other ingredients you should freeze. These are some of the perfectly suited foods for freezing in an ice cube tray.
-Homemade Stock
You can store about 2 tablespoons of stock and use it afterwards for reheating leftovers or making a sauce.
-Coffee
Did you notice that when you drink ice coffee, you get a coffee-flavored water? By storing coffee in the ice cube tray and later adding it to our coffee, you will get strong iced coffee.