Following the release of Windows 10 SDK preview build 17682 last week, Microsoft today pushed out SDK Preview build 17686 to developers. This release contains bug fixes and under-development changes to the API surface area and can be downloaded via the developer section on Windows Insider website.
There isn't anything much new with this build, as last week's release saw the addition of MSIX Support. Microsoft also removed some APIs from this build, and you can see more information on this by checking here.
Developers should take note that this build only works with previously released SDKs and Visual Studio 2017. It also will only work in conjunction with the latest Windows 10 Insider Preview build, which happens to be build 17866.
Microsoft is calling for feedback, so feel free to visit the developer forum once you've installed this latest SDK. The company also reminds developers that they can head to the Windows Platform UserVoice to request new developer feature requests.