Bring the cider and sugar to a boil in a saucepan. Boil the cider over high heat for 15 minutes. Do not cover the saucepan so that most of the alcohol can evaporate. Stir occasionally.
Bring a saucepan of salted water to a boil. Cook the spaghetti in salted water for 3 to 4 minutes.
Drain and rinse with cold water.
Now add the pasta to the cider. Reduce the heat and simmer for 5 - 6 minutes, stirring constantly, until the pasta has completely absorbed the cider.
Mix the pesto with the spaghetti and serve immediately. If necessary, season with salt and pepper to taste.
Tip: If you can`t get a green sauce pesto, you can replace it with a simple basil pesto. You can also enjoy the noodles straight.