First of all, we prepare a cup, and add half a cup of cold boiled water to it. We can't use cold water. It's unsanitary and easy to have diarrhea.
Then pour in a spoonful of brown sugar, and then add a spoonful of baking soda, and stir with a spoon.
Finally, add about three spoonfuls of white vinegar. If you can't eat it too sour, you can add less. Stir it, and a cup of delicious coke will be made. It will be even more delicious if it is chilled in the refrigerator!