A while back, once I realized it's a greeting not a question, I started answering with "so far so good". It's just as banal as "fine thanks" but it's non standard and makes people laugh. To be clear, I didn't intend it to be funny. Idk why people laugh, but I guess it's because it breaks the script in a gentle way. I honestly started saying it as a compromise between "fine thanks" and a genuine answer.

If I'm screwing with people I'll say "badly but I'm getting used to it".