Boil 1 cup (250 ml) of water in a kettle or saucepan.
In a coffee mug, add 1-2 teaspoons of instant coffee powder (depending on your preference for strength) and 1-2 teaspoons of sugar (optional).
Pour the boiling water into the coffee mug, filling it about 3/4 of the way.
Stir the coffee mixture well until the coffee powder and sugar are dissolved.
If desired, heat 1/4 cup (60 ml) of milk in a saucepan or microwave until hot but not boiling. Pour the hot milk into the coffee mug and stir to combine.
Serve the hot coffee immediately, and enjoy!