This may be slightly controversial, but I liked both 3's Sweet Treats and this idea. Actual gameplay more so, of course, I'd love an actual candyland.
We do technically have ice cream from Cool Kitchen and Lemonade is a mixer with the pitcher from Backyard Stuff and can run a bakery/ice cream shop with Dine Out/Get To Work retail, but I'd love more. I very much miss Sims 2's chocolate factory item and there are still gaps like a lemonade stand and oven for children. Plus those are good ideas for plants.
Maybe it could be part of that culinary quest survey idea from a while back? Personally, I'd like one centered on desserts as well, but hey.