With the ability to be open for anyone to edit, this can be a great tool to have the students contribute to a single activity. For example, I made a passé composé revision sheet. In this document, I give the instructions that I would like them to create sentences using the verbs I give them. I also model by creating the first sentence. Each student is expected to contribute one sentence and this can be monitored using the revision history option (to ensure things go smoothly). The goal is then to open this document the following day and go over the sentences checking if everyone understood the concept. The incorrect sentences can be corrected together.
In addition to that, the students get exposure to using Google docs in small doses and eventually learn to use them collaboratively when working on projects and other exercises. The ultimate goal is to familiarize them with this tool so that eventually it becomes the norm to work in this kind of environment.