Yummy in my tummy! Someone put these in my mouth right now!

4 large baking potatoes
1 pound ground beef
1 packet taco seasoning mix
1/2 cup water
1 cup shredded cheddar cheese
1/2 cup sour cream (optional)
Sliced green onions (optional)
Chopped tomatoes (optional)
Chopped cilantro (optional)