To add multiple users to your Sugarmate account, follow the below steps:
Tap the Menu button in the top left, then tap "signed in:" at the bottom of the menu.
Tap Add Another User
Log in (or create a new account) for the second user
You can then quickly switch between users by going back to the "Sign Out" window and tapping the user's name (instead of signing out).
A few important things to note:
1) Right now you can't see readings of both users at the same time
2) You can set different themes for each user, so you can more easily tell them apart (in Settings -> Display)
3) Go to Settings -> User and set a nickname for each user, so that will show up in the Sign out screen, and it will be clear who notifications are for
4) If you have an Apple Watch, you should use the same Apple ID and app-specific password for both accounts. Also, you can go to Apple Watch -> Advanced Options and turn on "Multi-user Support" so you can tell readings apart on the watch face. And if you use the Siri watch face, you can see both readings at the same time.