Sophie Cunningham must be a Juvenile fan ... 'cause the Indiana Fever guard was backin' that ass up after her squad won the WNBA Commissioner's Cup!!
The party went down on Tuesday after the Fever defeated the Minnesota Lynx with a 74-59 victory in the finale of the in-season tournament.
It was the first Commish's Cup win for the Fever ... and the champs certainly celebrated like it -- live streaming the whole bash on social media.