Favorite free things:

island ferry to see the Statue of Liberty Walk the grounds and the sanctuary of St. John the divine Explore Greenwood cemetary https://www.green-wood.com/visit/

For food since you have some time you can explore some of the places deeper in the outer boros.

New world mall in queens to have a bunch of good Chinese options

Get katchipuri in Brighton beach (a bread bowl filled with cheese) find a Georgian restaurant down there, Georgia house is good. While down there you could burn off the carbs and take a long walk to Coney Island for totonnos for a classic coal oven pie.

Nenes tacqueria for quesabirria. They just opened a second location on the border of park slope and sunset park or go to the original one in bushwick. I understand the lines at the one in bushwick are long though. Fucking amazing