If you have old bras that you don’t want anymore but are in good shape, donate them! Bras are one of the least donated and most needed items at domestic violence shelters across the US. Look up a local shelter and ask them if they’re accepting bra donations, and if they’re not, ask them who is! Check with homeless shelters and other charities!
Every year, the company I work for holds a large-scale bra donation campaign. My store collected almost a thousand bras to support women (and other breast-having people) in need.
DON’T THROW YOUR OLD BRAS AWAY.