Wash and dry the apples thoroughly. Remove any stems and insert a wooden stick into the top of each apple, pushing it about halfway through.
In a medium saucepan, combine the sugar, corn syrup, and water. Cook over medium heat, stirring until the sugar dissolves.
Once dissolved, stop stirring and allow the mixture to boil until it reaches the hard crack stage (300°F on a candy thermometer), about 10-15 minutes.
If using, add the red food coloring and vanilla extract once the mixture reaches the desired temperature. Stir gently to combine.
Remove the saucepan from heat and let it cool for a minute. Dip each apple into the hot candy mixture, swirling to coat evenly.
Allow excess candy to drip off before placing the apples on parchment paper or a silicone baking mat to cool completely.
Let the candy apples sit at room temperature for at least 30 minutes before serving to ensure the coating hardens.