Does the Garden have a café?

If I'm understanding your question correctly...The Nasher does have an excellent cafe and there is outdoor seating overlooking the garden.

There is a small cafe inside the museum, and it extends outside to the sculpture garden, which is my preferred place to eat. Note that the cafe isn't open the entire time the museum is open.

You can buy food and drinks from the cafe inside the museum and bring them to the garden. There are tables and chairs indoors and outdoors.

Coffee and wine

Yes it does.