I log into Stack Overflow (and others) using Google. I don't have any alternative means of login in many cases, like an email/password combination – Google is the only way of accessing those accounts.
Now the scenario is that I am on an untrusted computer and want to access eg. Stack Overflow. However, I don't want to log in to Google as I would put my primary email at risk.
How can I log in to SO/some other service anyway?
Best Answer
You can't. Stack Overflow recognizes you only because Google tells it who you are; and for that, Google has to recognize you first.
Alternatives:
Enable two-factor authentication for your Google account. Even if your password is stolen by a keylogger, it won't grant others access to your account.
Use a different account for authentication with less important sites that you will want to use casually at an airport / internet cafe. This may be too late if you already registered, but at least Stack Overflow (and Stack Exchange in general) allows you to add more credentials to your account.