How to Make Coffee Soda

What you need

• espresso machine
• V60 dripper
• V60 paper filter
• small saucepan or heat-safe vessel
• scale
• plastic bottle suitable for carbonation
• CO2 tank with carbonation cap
• temperature probe
• freezer
• squeeze bottle
• dropper bottle

Method

1. Make the 2-to-1 simple syrup: combine sugar and water in a 2-to-1 ratio by weight, heat gently until the sugar fully dissolves, then cool completely and transfer to a squeeze bottle.

   A 2-to-1 syrup is denser than a 1-to-1 syrup, so it adds sweetness with less additional liquid and less dilution.

2. Make the saline solution: dissolve 20 g of salt in 280 g of water, then transfer to a dropper bottle.

   Only a few drops will be used per serving; the remainder stores indefinitely.

3. Pull a double espresso using 19 g of ground coffee and collect 40 g of liquid yield.

   Lean toward a sweet, classic coffee character rather than a very fruity or funky profile.

   Expert tipA yield of 40 g from 19 g of coffee produces an espresso at approximately 9.5% strength, which is the target starting point before dilution.

4. Place an unrinsed V60 paper filter over a vessel and pour the hot espresso through it, allowing it to drain completely without pressing or stirring.

   The filter will clog as espresso fines block the paper — this is normal; be patient.

   Expert tipThis step is essential: crema and suspended particles act as nucleation sites for CO2. If they remain in the liquid, carbonation will escape violently on pouring. Paper-filtering through a V60 removes more insoluble material than pressing through narrow Aeropress papers under pressure.

5. Dilute the filtered espresso with approximately 180 g of mineral water to bring the total beverage to about 215 g.

   This dilution targets a final brew strength of approximately 1.5%.

6. Stir 30 g of the 2-to-1 simple syrup into the 215 g beverage, bringing the total to approximately 245 g.

   The 30 g of syrup contributes 20 g of sugar. Soft drinks can reach up to about 10% sugar, but this recipe uses less because the coffee contributes less acidity to counterbalance extreme sweetness.

7. Add a few drops of chocolate bitters and a few drops of saline solution; taste and adjust both additions carefully.

   The bitters should add a background bitterness and round out the finish — not taste citrusy or dominant. The saline should not register as salt.

   Expert tipBefore committing, test two or three chocolate bitters varieties in small poured samples and choose the one that is most subtle and improves the finish rather than pushing citrus to the front.

8. Transfer the beverage to a plastic carbonation bottle, squeeze out as much air as possible, attach a CO2-compatible cap, and chill in the freezer with a temperature probe until the liquid reaches approximately 2°C. Then carbonate by injecting CO2, depressurizing fully, and repressurizing once more.

   CO2 dissolves most readily in liquid at around 2°C; carbonating a warm liquid results in poor fizz retention. The depressurize-and-repressurize cycle drives out residual air and maximizes CO2 uptake.

   Expert tipPour slowly and gently when serving — coffee contains natural foaming agents that cause vigorous bubbling in a carbonated liquid.

Why this works

Paper-filtering the espresso before carbonating removes crema and suspended fines that would otherwise act as nucleation points, causing CO2 to escape rapidly and produce an unmanageably frothy pour. Chilling the liquid to approximately 2°C before adding CO2 takes advantage of the peak in carbon dioxide solubility at that temperature. Using a 2-to-1 simple syrup rather than a 1-to-1 syrup keeps sweetness additions concentrated, adding minimal extra water. A saline solution dosed below the perceptible threshold of saltiness enhances and lifts the overall coffee flavor.

Where beginners go wrong

1. 1

   The drink fizzes violently or becomes frothy when poured

   The espresso was not paper-filtered thoroughly enough. Suspended particles and crema create nucleation points that cause CO2 to come rapidly out of solution. Ensure the filtered liquid is clear before proceeding.

2. 2

   The V60 paper filter clogs and drains very slowly

   This is expected with espresso — the high concentration of fines blocks the paper. Do not press, stir, or agitate; simply wait for the liquid to drain through at its own pace.

3. 3

   Carbonation is weak or the drink goes flat quickly

   The liquid was likely not cold enough before carbonating. Chill to approximately 2°C and, after the first CO2 injection, depressurize and repressurize once more to minimize residual air and maximize CO2 absorption.

4. 4

   The bitters flavor is too dominant or tastes too citrusy

   Use far fewer drops — only a trace is needed. Sample different chocolate bitters varieties in small portions before adding to the full batch; choose the variety that is subtle and enhances the coffee's finish without introducing prominent citrus.

What you should taste

A refreshing, intensely flavored sparkling coffee with a satisfying amount of bitterness, a touch of acidity, and clean coffee depth. The chocolate bitters warm and round out the finish. The saline lifts and emphasizes coffee flavor without any perceptible saltiness.

FAQ