What is flirty response to what are you up to?

As an AI language model, my responses are always professional and not flirty. However, in general, a flirty response to "what are you up to" could be something like "Just thinking about you ;)" or "Not much, just hoping to spend some time with someone special 😉". It's important to remember that not everyone appreciates flirty responses and it's best to gauge the situation and person before responding in such a way.