Place carbonated water and cola in the refrigerator until very cold (about 30 minutes) if not already chilled. Cold liquids hold carbonation and create a better soda.

Flavor Syrup (Dr. Pepper–style)

make simple syrup

In a small saucepan, combine 0.25 cups water and 0.25 cups granulated sugar. Heat gently over medium-low heat, stirring, until the sugar fully dissolves and the mixture is clear (about 2–3 minutes). Do not boil. Remove from heat.

add flavorings

While the syrup is still warm, stir in 1 tablespoon black cherry syrup (or concentrated black cherry juice), 0.25 tsp amaretto or almond extract, 0.25 tsp vanilla extract, 0.5 tsp light molasses, 0.25 tsp orange zest, 0.125 tsp lemon zest, 1/16 tsp (0.0625 tsp) ground cinnamon, 1/16 tsp ground nutmeg, and a pinch (about 0.03 tsp) ground coriander if using. Whisk until evenly combined.

cool and rest

Let the syrup cool to room temperature, then transfer to a small jar and refrigerate for at least 15 minutes to let the flavors meld. The syrup can be stored in the refrigerator for up to 2 weeks.

Assembly & Garnish

Fill a tall glass with 1 cup of ice cubes.

Measure 2 tablespoons (about 30 ml) of the prepared flavor syrup and pour it over the ice. (Note: this recipe yields a Dr. Pepper–style soda for 1 serving; adjust syrup amount to taste between 1–3 tablespoons.)

Pour 1/2 cup chilled cola into the glass over the syrup, then slowly add 1 cup chilled carbonated water. Stir gently once to combine, taking care not to flatten the carbonation.

Garnish with 1 maraschino cherry and half a lemon wheel or an orange slice on the rim or in the glass.

Serve immediately with a straw. Taste and adjust: if you prefer a sweeter, fruitier soda, add another 1/2–1 tablespoon of flavor syrup; for more vanilla or almond notes, add a tiny pinch more extract to the remaining syrup.