I have created a Google Cloud Function through functions.https.onRequest, which is working nicely when I paste its URL in a browser and integ
firebaser here
Update: There is now a client-side SDK that allows you to call Cloud Functions directly from supported devices. See Dima's answer for a sample and the latest updates.
Original answer below...
@looptheloop88 is correct. There is no SDK for calling Google Cloud Functions from your Android app. I would definitely file a feature request.
But at the moment that means you should use the regular means of calling HTTP end points from Android: