Here's my implementation, I'm storing the baseURL on my firestore database. I used to sign in anonymously in order to get the url. But on calling the firestore, my app crashes without any error, warning, etc.

import {create} from 'apisauce';
import auth from '@react-native-firebase/auth';
import firestore, {firebase} from '@react-native-firebase/firestore';

const apiClient = create({
  method: 'POST',
});

apiClient.addAsyncRequestTransform(async request => {
  await auth()
    .signInAnonymously()
    .then(() => {
      console.log('success');
    })
    .catch(error => {
      console.log(error);
    });
  const url = await firestore()
    .collection('service_url')
    .doc('service_url')
    .get()
    .then(document => console.log(document.data))
    .catch(error => console.log(error));
  console.log(url);
  request.baseURL = url;
  auth().signOut();
});

export default apiClient;