Windows 10 sdk offline installer?
Solution 1:
There is no offline installer/ISO since Windows 8. Go to a PC with a fast unlimited download, run the Installer and select Download the SDK - Windows 10 10586 for installation on a separate computer
This downloads all files and you can use tools like Folder2Iso to create an ISO based on the folder to use it on different PCs.
Solution 2:
Windows 10 SDK offline installer is available from this link.
You can download the ISO and use it for offline installation. Its size is 643MB.