Home -> cog wheel at the bottom of the menu -> scroll down to bottom of settings and press log out. The initial menu comes up and you can chose between 'Facebook' and 'Google Play'. If you already have a team on FB account then create a Google Play ID and you can have a second team on Google. It's just a case of switching between FB and Google using the Logoff system...
The only issue is if both teams have a match at the same time - usually I attend the match which is the most important and let the other team go on auto-pilot...