Also understandable, I don't want to spend $3 every day on coffee I don't really want to drink while feeling bad about taking up table space.
ZOnks! Why not go to the library? The public library has many many large tables, and old school supportive wooden chairs, and FREE WI-FI! There is even a dedicated laptop table with a power strip at my library.
So I come here 2-3 days a week, its a short walk from my house, so I have a reason to leave and walk in the sunshine. They let you bring your own snack/drinks and they are filled with interesting people. You might be here right before toddler time starts and the place is filled with 2 year olds, waiting to be called into the conference room. You can watch the old men who come every day swap copies of the New York Times and the New York Post. There are the teenagers who come in to play video games for hours. All in all it is fairly lively.
Check out Brooklyn library location and hours here.