Combine 2 cups granulated sugar and 1 cup water in a small saucepan over medium heat. Stir until sugar fully dissolves and the mixture comes to a gentle simmer.

Add flavorings

Lower heat to medium-low. Stir in the caramel color (or add prepared caramel) until evenly incorporated to achieve a cola-brown color. Add 1 tsp white vinegar (as a phosphoric-acid substitute), 1 tsp fresh lemon juice, and 1 tsp citric acid (if using) to provide acidity. Stir to combine.

Spice and aromatic blend

Add 1/2 tsp vanilla extract, 1/4 tsp citrus oil blend (or a few drops concentrated cola flavoring), 1/8 tsp ground cinnamon, 1/16 tsp ground nutmeg, 1/16 tsp ground coriander, 1/2 tsp grated fresh ginger, and 1/2 tsp pineapple juice. Stir well. Keep the mixture at a low simmer for 2–3 minutes to allow the flavors to marry, stirring occasionally. Do not boil vigorously — gentle heat is sufficient.

Cool and strain

Remove the syrup from heat and let it cool to room temperature. If you added fresh ginger or used any solids, strain the syrup through a fine mesh sieve or cheesecloth into a clean container to remove solids. Taste and adjust: add a little more acid (vinegar or citric acid) if it needs more tang, or a touch more sugar if too tart.

Concentrate ratio note

This syrup yields a concentrate intended to be mixed with cold sparkling water at about a 1:4 syrup-to-water ratio (by volume). Adjust to taste — some prefer 1:5 for a lighter soda.

Assemble and serve

Chill: Ensure your sparkling water is well chilled. For best fizz, keep both syrup and sparkling water cold and mix immediately before serving.

Mix: For one serving (~1 cup finished soda), combine 1/4 cup cola syrup concentrate with 1 cup cold sparkling water in a glass. Stir gently once or twice to combine without losing too much carbonation.

Serve: Add ice if desired and garnish with a lemon or lime wedge. Serve immediately.

Storage: Store unused syrup in a sealed container in the refrigerator for up to 2 weeks. Keep refrigerated and stir before use.