GISHWHES overlord and actor Misha Collins posted this to Facebook today. The comments on the post is positively riddled with menstrual cup evangelists insisting that he should ask people to donate cups instead.
Why does it have to be one or the other? If you want to donate a diva cup, donate a diva cup. But also bear in mind that a lot of women might not be interested in trying some newfangled menstrual product when they have more pressing things to worry about like finding a job and a safe place to live, and maybe making sure their kids are eating today. The women should have the option to choose, rather than just getting stuck with what some stranger thinks is most virtuous.
Also, menstrual cups have a bit of a learning curve, and having an accident while wearing one when you don't have easy access to laundry facilities would also be problematic.
(Incidentally, yes, in case you are wondering, people also brought up the issue of the Salvation Army and LGBTQ rights.)