With short kitchen skewers, popsicle sticks or single chopsticks, spear each apple through the stem end until the skewer is about halfway down each apple. Line a baking tray with parchment paper. Set a pastry brush and a small dish of water next to the stovetop.
In a small, heavy-bottomed saucepan, add the sugar and ½ cup (120ml) of water. Set over medium-low heat and, stirring constantly with a heatproof silicone spatula, gently heat to dissolve the sugar. When the syrup is liquidy but before the sugar is dissolved, add the food colouring and stir to combine. Make sure to avoid letting the syrup come to a boil before it is completely dissolved. If you fear the syrup is heating too quickly, remove it from the heat periodically, if necessary, until the sugar is completely dissolved.
Stop stirring immediately as soon as the syrup begins to simmer. Using the pastry brush, dip it in the water and wash down the sides of the pan to get rid of any sugar crystals or set sugar.
Allow the sugar to boil for about 15-20 minutes, or until an instant-read thermometer (or a candy thermometer) registers at 300°F (150°C) - also known as the hard crack stage (see note 2).
Take the pan off the heat and wait for a few seconds for the bubbles to subside. Then, working quickly, dip each apple in the syrup to coat them thoroughly and set them on the prepared parchment paper to set. If the sugar syrup begins to set up before you are finished dipping the apples, simply set the pan over low heat to melt the syrup again.
Allow the apples to set for a few minutes before eating.
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Notes
1. I find caster sugar (also known as superfine sugar) to be the most effective when making any kind of candy without corn syrup as it dissolves a bit quicker and more efficiently. However, this can easily be made with regular granulated sugar if that is all you have.2. If you don't have a thermometer, keep a small dish of ice water next to your stovetop. Once the steam has subsided on your sugar syrup (roughly 10 minutes in), put a small drop of the syrup in the water. Once it sets to a brittle, hard candy texture, you know that you've hit the right temperature.