In a large stockpot or Dutch oven, saute the garlic and olive oil over medium heat, just until fragrant, about 1 minute.
Add remaining ingredients except for salt, pepper, and sugar. Bring marinara to a simmer over medium high heat. Reduce heat to medium low, cover the pan, and cook for 30-45 minutes.
Discard the basil leaves. Taste the sauce and add sugar, salt, and pepper to taste.
