Bring water to a boil, cook pasta according to directions.
Chop tomatoes, mozzarella (if using), basil, and olives.
Combine chopped tomatoes, cubed mozzarella (if using), basil, olives, vinegar, salt, and pepper in a large bowl.
Once the pasta is done cooking, drain the water and add the pasta to the tomato mixture and gently toss to mix.
Heat olive oil in a small frying pan over medium heat. Add garlic and cook, stirring constantly, for about 1 minute until fragrant.
Pour the oil over the pasta and tomato mixture and toss again to mix well.
OPTIONAL: If you choose to add chicken, cube chicken and cook in a pan until internal temperature is 165 degrees Fahrenheit. I like to add flavor to the chicken with garlic powder, sea salt, pepper, onion powder, and Italian seasoning (about 1⁄2 tsp each). Add to spaghetti mixture.