Is this place really called the "Sandwich Inn"? I've always just known it as Goodman's.
In any case, I have been going there since I was child. My parents got me hooked on corned beef at a young age, and let me tell you something else: PICKLES.
The short bar with its little stools has probably been there since my dad was a boy - the decor has not been renovated, it doesn't seem - which is seriously awesome, if you ask me. It's like going back in time to an old diner. Except it's now. And everything is old. There is a place to hang your hat on the wall. So, you know, wear your hat.
The food's great, the staff is hilarious. They serve the champagne of beers. Really, it's heaven on earth. In an ironic sort of way. But seriously.
I recommend following up your lunch with a trip to Jack Frost Donuts down the street, for an Old Brooklyn culinary tour.