Preheat the oven to 350 and lightly butter the pans.
Use an electric mixer or hand mixer to cream the butter and sugar.
When it is creamy, add the eggs and mix thoroughly.
With the mixer on low, pour the milk in a little at a time.
When all the milk is in, add the baking soda and then slowly add the flour one cup of flour at a time and mix well between cups.
Divide 1/2 of the batter evenly between the two lightly buttered pans.
Make them about as equal as you can. If you use a little less than half of the batter that's OK.
Now use about 3/4 of the cinnamon sugar (that's about 4 1/2 Tablespoons per loaf) to sprinkle the top of each loaf and swirl with a knife.
Divide the remaining batter between the two pans and sprinkle the rest of the cinnamon sugar onto their tops and swirl. Be sure to do tight swirls so you don't introduce air into the batter.
Bake at 350 for about an hour.
Stick a knife in to check for doneness. If the knife comes out with gooey batter on it, leave it in for 5-minute increments until the knife comes out clean, this means it is done.
Let the pans cool on a rack for 20 minutes before you remove them from the pan and cut them. If you don't, the loaf falls apart when you cut it.