If your school allowed it and you were able to do it at a profit, then yes you could.
Roadrunner Sports does sell womens sports bras online from their website. They are really expensive though you could probably get the same thing cheaper from Walmart.
You could try donating it to a school or possibly sell it on Ebay.
You can find numerous sites that sell positive promotions. There are sites that sell promotions that is relevant to what you need them for, for example: school, sports, jobs, and business.
marshmallows or doughnuts
There are companies that sell school signs to the public, but they need to first obtain permission from the school or else they could get into deep legal trouble.
How and where do you apply for a license to sell retail sports clothing?
You could try asking at a sports shop, if they don't sell them, they could probably give you an address of where you can. Failing that you could try ebay.
they could sell art, or other goods, or they could die.
Yes, they do sell camping accessories. They also sell a lot of other goods that have to do with being active. Sports Authority specializes in sports, but also most likely meet your camping needs.
to sell sports clothing and equipment, and make money.
Boat House Sports sells goods for people that play sports. They sell clothing, gear, uniforms, and accessories for both players and coaches. They accommodate most all sports.