WPMU have published a guide on how to backup to Google Drive, as their “weekend WordPress project”. You can see it here.
Alternatively, our own guide is here: http://updraftplus.com/support/configuring-google-drive-api-access-in-updraftplus/
Setting up Google Drive is not the easiest (Dropbox is) – Google’s setup gives you with a few hoops to jump through. But, as the WPMU guys say, it’s not hard either. And on the other hand, they do give you 15Gb for free. Once you’ve done it a couple of times, it starts to make sense.
If you get stuck, then there’s a “Google Drive” section in the FAQs (and our setup guide mentions the most common mistakes at the relevant points too) – so do double-check; Google Drive is very popular, so the chances of you coming across something that’s not been come across many times before and documented in there is very low.
David Anderson (founder, lead developer, UpdraftPlus)