A cold brew tonic over ice with a slice of orange

Cold Brew Tonic

A cold brew tonic is 45 ml of concentrate poured over 120 ml of tonic and a full glass of ice. Coffee goes in last, and that order is the...

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Recipe · 3 min

Cold Brew Tonic

Coffee and quinine sound like a bad idea until you have had one at four in the afternoon in May, when Delhi is sitting at 43°C and nothing else appeals. The bitterness in tonic and the bitterness in coffee are different bitternesses, and they do not fight. What you get is dry, cold, faintly citrus, and far more refreshing than either drink alone. It takes three minutes and it is almost impossible to get wrong, provided you pour in the right order.

The short answer

Fill a tall glass to the brim with ice. Pour in 120 ml of very cold tonic water. Add 45 ml of cold brew concentrate slowly over the back of a spoon so it settles in a dark layer. Squeeze in a wedge of lime, stir once, drink. Roughly 1 part coffee to 3 parts tonic. Coffee always goes in last.

Cold Brew Tonic

1:3 coffee to tonic · 3 min
Step 1
Get everything properly coldGlass in the freezer for ten minutes. Tonic straight from the back of the fridge, not the door. Concentrate cold, not room temperature. Every degree you save here is a sip you do not lose to melting ice.
Step 2
Fill the glass with iceAll the way to the rim, and use the biggest cubes your tray makes. A half-filled glass melts faster, not slower — less ice means more surface area per unit of mass exposed to warm liquid. In a 300 ml glass that is roughly 150 g of ice.
Step 3
Tonic in first, 120 mlPour it down the inside wall of the glass at an angle. Straight down the middle onto ice knocks the carbonation out in seconds, and flat tonic tastes like sweet quinine syrup.
Step 4
Coffee last, 45 ml, over a spoonHold a teaspoon upside down just above the tonic and pour the concentrate across it. Cold brew is denser than tonic, so it will sink slowly and layer. Doing it the other way round — tonic onto coffee — makes the glass foam over and go flat before you have finished pouring.
Step 5
Lime, one stir, doneA wedge of Indian lime (nimbu), squeezed and dropped in. One slow stir from the bottom, no more. Over-stirring is the second most common way to end up with a flat drink.
Adjust
Dial the ratio to your concentrateIf your cold brew was brewed at 1:5 it is strong; stay at 45 ml. If you brewed at 1:8 it is closer to ready-to-drink, so push to 70 ml and cut the tonic to 100 ml. Taste, then change one number at a time.

Which tonic, and which coffee

Tonic is not a neutral mixer. It carries sugar, quinine and citrus oils, and the brand you pick moves the drink more than the coffee does. Most Indian supermarkets and quick-commerce apps now stock four or five, and they behave differently enough that you should adjust the coffee dose to suit.

Tonic How it drinks with cold brew
Schweppes Indian Tonic Water The sweetest and softest of the lot, quinine well in the background. Forgiving, widely available, and it will flatter a chocolatey coffee. Drop to 40 ml concentrate or it turns syrupy.
Svami Indian Tonic Drier, more assertive quinine, holds its fizz longer than most. The best all-round choice here. Full 45 ml.
Sepoy & Co Indian Tonic Citrus-forward and light on sugar. Excellent with a fruity Chikmagalur or Araku lot; skip the lime, it is already there.
Plain soda water Not tonic. No sugar and no quinine means no structure — you get cold, fizzy, slightly sour coffee. Fine if you want that, but it is a different drink.

On the coffee side, this is not where you put your darkest roast. Roasty and smoky notes turn ashy against quinine. Use a light or medium filter roast with acidity to spare — a washed Arabica from Chikmagalur or Coorg, or anything with citrus and stone fruit in the cup notes. Our single-origin lots are labelled with what they actually taste like, which makes this easier than guessing.

Making the concentrate

You need cold brew concentrate, not diluted ready-to-drink cold brew, or the tonic will thin it into nothing. Brew at 1:5 by weight — 100 g of coarsely ground coffee to 500 ml of filtered water at room temperature, steeped 16 to 18 hours, then filtered. In a Delhi summer kitchen where the ambient temperature sits near 35°C, cut that to 12 to 14 hours or brew it in the fridge for the full 18. Full method and grind settings are in the cold brew guide.

Concentrate keeps about ten days in a sealed bottle in the fridge. Past that it flattens out and starts tasting papery, which no amount of tonic hides.

Questions

Cold brew tonic, answered

Why does the coffee have to go in last?

Two reasons. Carbonation escapes fastest when liquid is poured onto liquid with force, so pouring tonic onto coffee makes the glass foam and go flat. And cold brew concentrate is denser than tonic, so poured gently on top it sinks in a layer rather than mixing instantly, which gives you the look and lets you control the mix with a single stir.

Can I use instant coffee or a moka pot instead of cold brew?

Instant works in an emergency but tastes cooked against quinine. Moka pot is better — brew it, cool it fully in the fridge first, and use about 40 ml. Never pour hot coffee into tonic; the heat strips the carbonation instantly and you get a warm, flat, bitter glass.

My drink tastes bitter and medicinal. What went wrong?

Usually too much concentrate, or a dark roast. Quinine bitterness and roast bitterness stack. Cut the coffee to 35 ml, switch to a lighter roast, and add the lime — acidity cuts through both.

Should I add sugar?

Tonic already carries 8 to 10 g of sugar per 100 ml, so almost certainly not. If you want it sweeter, use a sweeter tonic like Schweppes rather than adding sugar syrup, which makes the drink heavy.

Does it work with milk?

No. The acidity in tonic curdles milk. If you want cold coffee with milk, make an iced latte instead.

Built for the hot months

Bright, fruity lots that hold up against tonic.

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