If using granular erythritol or allulose, combine 1/4 cup of erythritol/allulose with 1/4 cup hot water in a small jar, stir until dissolved to make a 1:1 simple syrup. Chill before using. For this recipe you will use approximately 0.5 fl oz of that syrup. If using a liquid nonnutritive sweetener (sucralose or stevia liquid), skip this step.

Mix concentrates and flavour

In a measuring glass or small pitcher combine the 1 fl oz espresso (or 1 fl oz cold-brew concentrate) and 1 fl oz green tea concentrate (or matcha solution). Stir to combine.

Add 0.5 fl oz erythritol/allulose syrup (or omit and use additional liquid sweetener as needed), 3 drops liquid sucralose (taste and adjust; add more drops if you prefer sweeter), and 1 tsp fresh lemon juice. Stir until fully blended.

Add 1 drop citrus extract and a pinch of salt. If using taurine or B-complex powder, add them now and stir vigorously until dissolved. Note: ensure any supplements used are food-grade and measured carefully.

Assemble drink

Fill a 12–16 fl oz glass with 1 cup ice. Pour the chilled carbonated water (8 fl oz) over the ice.

Slowly pour the prepared concentrate mixture over the carbonated water. Pouring slowly preserves carbonation and creates a light layering.

Gently stir 2–3 times with a bar spoon to integrate without flattening the soda.

Garnish with a thin lemon wheel or a strip of lemon zest. Serve immediately.

Taste adjustments & notes

If the drink is too tart, add another drop or two of sweetener or 0.25 fl oz more simple syrup. If it tastes flat, use colder carbonated water and pour more gently. Adjust caffeine level by varying the espresso/cold-brew amount; do not exceed your personal tolerance.