Heat 1 tablespoon olive oil in a skillet over medium heat. Add sausages and cook until browned and firm, about 10 minutes. Cut sausages into 1/2 inch slices, return to the skillet, and continue cooking until no longer pink. Drain sausage slices on a paper towel-lined plate.

Meanwhile, heat 1 tablespoon olive oil in a saucepan over medium heat; stir in onion and cook until the onion softens and turns translucent, about 5 minutes. Add garlic and 1 1/2 teaspoons Italian seasoning; cook until the garlic softens, about 2 minutes.

Pour in crushed tomatoes, water, salt, sugar, and remaining 1 tablespoon of Italian seasoning. Bring to a simmer, then reduce heat to medium-low, cover, and simmer for 20 minutes.

Bring a large pot of lightly salted water to a boil. Add gnocchi and cook for 2 to 3 minutes until pasta floats; drain.