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Mix equal parts condensed milk and half-and-half in a mason jar. Sprinkle in your flavorings. Shake your jar to mix. Chill before serving.
How much you should use depends on how much creamer you want. Use the jar you choose as your guide, adding as much as can reasonably fit in the jar. Make sure you have the same amount of condensed milk and half-and-half.  Make sure you leave about an inch of headspace. The measuring does not have to be completely precise, but it can be a good idea to use measuring cups here. Measure out the cinnamon and vanilla extract. Pour the spices in with the milk and cream mixture. Seal your jar tightly to prevent leaking. Give the jar a good shake. Shake for a few seconds to mix everything evenly. The creamer will taste best after it's been chilled. Place it in a refrigerator for at least an hour before adding it to coffee. The creamer will last about as long as the expiration date indicated on your milk and half-and-half.