>Well, I can only say thanks to wikihow.com and copy the full text in here:
3.50 ml orange oil
1.00 ml lemon oil
1.00 ml nutmeg oil
1.25 ml cassia oil
0.25 ml coriander oil
0.25 ml neroli oil
2.75 ml lime oil
0.25 ml lavender oil
10.0 g gum arabic
3.00 ml water
2.00 tsp (10 ml) flavoring
3.50 tsp (17.5 ml) 75% phosphoric acid or citric acid
2.28 l water
2.36 kg granulated white sugar
0.50 tsp (2.5 ml) caffeine (optional. use caution)
30.0 ml caramel color
Mix the oils together.
Add gum arabic and mix completely.
Add water and mix well. For this step, use a hand mixer or blender to thoroughly mix together.
The flavoring can be made in advance and stored for use later. Place in a sealed glass jar and place in the refrigerator or keep at room temperature.
Mix 5 ml of flavoring with the phosphoric or citric acid.
Add the water and sugar and, while mixing, add caffeine if desired.
Make sure that the caffeine is completely dissolved before moving on to the next step.
Mix one part of concentrate with five parts water. In other words, however much you use of the concentrate, use five times as much of water.
Carbonate the beverage.There are a few ways this can be accomplished:
Mix soda water directly with the concentrate, as described in the previous step
Use a soda fountain that will combine the concentrate with carbonated water at the tap
It can be difficult to find all the different ingredients. They are not always available in supermarkets. Try looking at local specialty shops in their baking section.
Don’t confuse this homemade recipe with the the canned cola that’s been distributed at trade shows and through other venues or outlets. While the recipe is the same, the process of canning soda is beyond the scope of this article.
!!! Warnings !!!
Caffeine can be toxic in high doses. Be careful not to add too much to your mixture, and do not ingest large quantities.
Many of the oils needed for flavoring can burn skin. Use caution when preparing. They can also dissolve the plastic lining of a refrigerator; store with caution.
Gum arabic is available in two forms, art grade, and food grade. Be sure to get food grade Gum arabic, or you could have an unpleasant toxic reaction.