Combine 2 cups granulated sugar and 1 cup water in a small saucepan. Heat over medium, stirring until sugar fully dissolves. Bring to a gentle simmer for 2 minutes to integrate, then remove from heat.

Stir in 2 tablespoons caramel color while the syrup is warm so it blends evenly. Set syrup aside to cool to room temperature.

Acid balance & flavorings

Once the syrup is cooled, stir in the citrus juices (1 tablespoon fresh lime juice and 1 tablespoon fresh lemon juice). Mix thoroughly.

Add 1/2 teaspoon of a 10% phosphoric acid solution (or a comparable small amount of dissolved citric acid) to bring the sharp cola tang. Stir well and taste carefully; acids are potent, so add gradually if you need to adjust.

Stir in 1/2 teaspoon vanilla extract. If using powdered caffeine, dissolve the 50 mg in a teaspoon of warm water first, then add and stir until fully dissolved (optional).

Essential oils & flavor concentrate

Prepare the essential oil blend accurately. In a small neutral-tasting spoon or dropper, add the oils in the order listed: 6 drops orange oil, 2 drops lemon oil, 2 drops lime oil, 1 drop nutmeg oil, 1 drop cinnamon oil, 1 drop coriander oil, 1 drop neroli/orange flower water. Because essential oils are highly concentrated, measure precisely.

Emulsify the oils into the syrup: take a teaspoon of the cooled syrup and whisk the oils into it until you have a smooth, uniform mixture. Then whisk that emulsified paste back into the main syrup until fully incorporated.

To serve

Chill the syrup thoroughly (at least 1 hour) before mixing with carbonated water. For serving, mix 1 part syrup to 4 parts chilled carbonated water (example: 1/2 cup syrup to 2 cups soda water) into a pitcher or individual glass, adjusting to taste.

Add ice to glasses, pour the mixed cola over ice, and garnish with a lime or lemon wedge. Serve immediately.

Store unused syrup in a sealed container in the refrigerator for up to 2 weeks. Shake well before using, as natural oils can separate.