Not sure how many charities do that, but I've seen some. For example, Jo's Cervical Cancer Trust is proposing fundraising by clearing out your wardrobe (selling clothes on depop/Facebook/eBay etc to fundraise) or doing a fitness challenge.
I know some of you are probably busier than ever with the family at home, but for those who are desperately looking for something to do it seems like a nice idea! I might get rid of all the clothes I kept in case I get skinny again (which I probably won't especially after all the snacking now).