I used to think the Google Docs was completely unusable because I could get neither the fraction of superscript/subscript options to work. Then I found this video which explains that you have to use the tab key to switch from numerator to denominator in a fraction and the right arrow key for superscript/subscript.
You can also use LaTeX shortcuts for many things as explained here. On a Mac I found (by trial and error) that I have to type "alt-^" instead of "^" to get superscripts. So the first equation in the video can be entered as
\Sigma [space] \frac [space] 1 [tab] 2 [right arrow] mv [alt-^] 2
Either way the end result looks awful, but it's better than nothing.
This work is licensed under a Creative Commons Attribution 3.0 Unported License.