http://e26whn2524322mkxb3cbyk27ev2ihhq2biz35hty7gzgsyrwrygq27yd.onion/posts/blog/the-internet/moving-on-from-google-apps-for-domains.html
you're then pretty much at the mercy of whether the connected application lets you switch out Google accounts. Some don't, but some can be worked around (Pokemon Go, for example, you can apparently link your Facebook account, unlink the old Google account, link a different Google account, then unlink Facebook).