You can use this template as a set of guidelines to design VR interfaces in Sketch and test it in context using the free GoPro VR Player How to use the template:
1 - Download the Sketch template
2 - Replace the background with an equirectangular image (you can find some online)
3 - Design your interface within the area defined in the middle of the 360 canvas
4 - Export your artboard as a PNG or JPEG
5 - Drag and drop your exported image into GoPro VR Player Et voila!
If you own a VR headset you can plug it to your computer and use it with the GoPro VR Player for an immersive VR preview. Have fun!