I usually try to repackage any unwanted items we get into a new mishloach manos to give out (obviously not to the original giver, but it ends up being a mishmash anyway so I’m not sure it matters).
With candy, we each take what we want out of our own shalach manos and then pool the rest together for a Shabbos grab bag for when little kids come over.
We don’t really throw things away- if we don’t want it, someone else probably does.