In most cities social services and red cross will help. Here in southern Fl. CROS ministries tries to help out.
Please look for ministries or nonprofit agencies to donate. Ask if they sell their items. The clientel at the Caring Kitchen in Palm beach has no money.

Clothes are complicated. There are tons of clothes people have they would donate and there are tons of people who need clothes. But clothes come in a huge variety of styles and sizes and it is like looking for a needle in a haystack for a person to try to find top, bottom, and all the other components appropriate for the the climate, the season, their gender, their size, their personal style (this is VERY important when someone homeless!) and have all the right parts (right underwear, right socks, right belt, ect.) in colors that look ok together and don't look stupid making the person feel even worse. The classic sad clown costume is basically the get up of a homeless person. You can dress like that or wear the same thing all the time till it is filthy or both. I have been homeless, luckily for me, for short periods.
About all the laundry truck people might be able to do is pass out generic new stuff like T-shirts and cotton drawstring pants in small, medium, and large. Not very green though, and makes no use of the billions of garments available for donation. To get donated clothing to the right person requires great organization, huge amounts of clean dry storage complete with hangers and racks as well as laundry facilities, and most of all, many volunteers putting in many hours to process the clothing. We really need to organize all the clothing donation/distribution efforts into a central national thing or even world wide.