ngspice for cuda may be compiled by MS Visual Studio Community 2015.
VS 2017 is not compatible with cuda 8.0 (you will have to wait for 9.0).

For compilation you need the GNU bison parser generator.

A ready for windows compiled variant can be downloaded as
  win_flex_bison-latest.zip
from
  http://sourceforge.net/projects/winflexbison/files/

Create the directory
  ../../flex-bison
relative from this directory right here, and unzip there.

We will invoke the win_bison.exe file
 in this directory during the visual studio compilation.
 
Install CUDA 8.0 from 
https://developer.nvidia.com/cuda-downloads

Visual Studio is started by double click on cuspice.sln.
Select 'Build' 'Configuration Manager' and then choose one
of the build options, e.g. 'Active solution configuration'
with its Debug or Release GUI versions or the
equivalent console version (no GUI, no graphical interface),
and 'Active solution platform', generating 64 bit code only.

XSPICE and CIDER is not supported by cuspice.

Installation procedure will generate the following tree:

C:\Spice64\
    bin\
        ngspice.exe
        vcomp140.dll
    share\
        ngspice
            scripts\
                spinit

C:\Spice64\ may be renamed to any folder with rights for read and write.
If spinit is not found in the directory cited above,
ngspice.exe also searches for spinit in its own directory.