I have used Jan Kruegers guide along with Sqouzen and Open Cola to find the correct ratios needed. Jan's recipe was chosen because its sugar free and skips the step with making sugar syrup, and you end up with 257ml syrup that gives 45l cola.

I'm on the fourth 1/4 scale batch, and weigh everything because its more precise than measuring volume, and that have helped me dial in the correct amounts.

I found that it's fun it is to tinker with all the ratios in a spreadsheet, while dialing in the recipe to my taste.

Even Coke got rid of the kola nut, so the caffeine is purely optional at this point. Other than the caffeine, all it offered was a bitter flavor that needed to be offset by sugar and acid.

Edit: though caffeine itself is also bitter so you can't just completely remove it without either significantly modifying the recipe or adding a bitter replacement