We're still waiting to see if Microsoft pushes out a new Windows Insider Fast Ring build today, but in the meantime you can download and install the Windows 10 SDK Preview Build 17046. The new SDK catches the software development kit up with the latest current Windows 10 Fast Ring Insider release.
The SDK, like other preview builds before it, requires Visual Studio 2017, and is intended to be run on a Windows 10 Insider build. Anything else is not supported and may fail.
There are a few gotchas in the new SDK, if you're using it to build and/or test apps, you should read the blog post for more information.