Preheat oven to 375 degrees.
Mix cheeses, eggs, garlic powder, salt, and pepper together. Add drained spinach and mix.
Using a piping bag or Ziploc bag with plastic coupler tip, pipe filling into each uncooked manicotti noodle. Place in a 9x13-inch baking dish.
In a large bowl or pitcher, mix spaghetti sauce and hot water. You want enough sauce to cover the pasta. Pour over stuffed pasta noodles. It will be very liquidy. The pasta will absorb most of the liquid when baking.
Cover with tinfoil and bake for 45-50 minutes until the liquid is mostly absorbed and pasta is cooked through.
Garnish with cheese and fresh basil.