I enjoy baking, and on a number of occasions have baked cakes or other desserts for people in the office to celebrate their birthday or a work-related milestone. I've done this of my own accord, without being asked. I don't do this for every birthday or milestone, and it's usually related to me wanting to practice a recipe, or express gratitude to someone.
Last week, I overheard a co-worker saying that I'd be baking a cake for a milestone they were close to hitting. I had never said such a thing, I had no plans to do so. When he approached me to "suggest" I bake a cake for the milestone, I said no, and he responded, "But you like baking, so just bake a cake for us."
Baking is a hobby for me, but it's also time-consuming, and can get expensive for some things just with the cost of ingredients. The title is a bit misleading, as it's not so much about the free part - I don't want to do it in exchange for money. It's more about the time aspect for me - time spent baking is time not doing other things I enjoy.
How do I explain to my co-worker that I don't want to bake a cake for his milestone? I'm finding it a bit tricky as I have set a precedent of baking things in the past.
Edit 5th Oct 2023: I had forgotten about this question until now, but thought I'd give an update. I didn't end up baking a cake for the milestone. The co-worker brought it up one more time after I posted this question, and I reiterated my "No" answer with no further elaboration. I did feel a bit bad and ended up cutting down on my baking in general so as to not make him feel singled-out. We are still in good terms.
There's been a lot of turnover since then and I am no-longer known as The Baker - a reputation I am glad to have shed to avoid future encounters. Now I just leave things anonymously in the different kitchens in our office building.