Add your Italian sausage to a large soup pot over medium-high heat. Break it apart with your spoon as it cooks, letting it get nicely browned all over. This should take about five to six minutes total.
Toss in your chopped onion and minced garlic right into the same pot with the sausage. Cook for another five minutes, stirring occasionally, until the onion turns soft and translucent. Drain off any excess fat if there's a lot sitting in the pot.
Pour in your chicken broth and water, then add the bell pepper, celery, and diced sweet potatoes. Give everything a good stir so the vegetables are evenly distributed through the liquid before you turn up the heat.
Bring the pot to a boil over high heat, then reduce it down to a simmer. Cover with the lid slightly ajar and let everything cook for fifteen to twenty minutes, until the sweet potatoes turn fork-tender.
Taste your soup and add salt and pepper as needed, since the sausage and broth bring different amounts of saltiness depending on the brand. Ladle it into bowls while it's hot and serve right away.