I work in nonprofit fundraising and have gotten so many shirts, mostly ugly and ill-fitting. It's hugely wasteful. Kids summer camps also love to give you a "free" t-shirt.

The soft ones get saved to be used as pajamas, the rest go to textile recycling.

Sleep shirts and eventually donate.

I keep a lot of them, but in a pile in the closet if they're not ones they wear in daily rotation. They come in handy for "you need a yellow shirt for field day tomorrow!" or "tomorrow is rainbow day - the whole 4th grade should wear orange!" I weed out the pile occasionally for sizes/too many of one color/extreme ugliness/etc.

They wear them. What else would you do with them? Get rid of them if they don't want them.

You wouldn't believe how much trouble people gave my kids when they tried to refuse them.

One camp counselor zipped one into my son's backpack after he refused it 3 times on 2 different days.

Sleep shirts.

Same. Save and have made into a blanket.

I had them made into a blanket that my son put on his bed.

Summer camps
And rec sports.

My Ds won’t wear them as they are usually scratchy and don’t fit well. They wind up as rags in the garage.

We decline a lot of them. My kid just won’t wear them.

Summer camps, sports teams, summer swim events, 5k and other races/competitions. We keep them. DC wore them a ton until he was around 13, now he prefers to wear plain solid-colored shirts but likes to have a shelf full of souvenir shirts.

When my son graduated from high school, I had many of them made into a T-shirt quilt. He loves it!

Bar and bat mitzvahs, keep them

Which activities and extracurriculars spawn the most t-shirts, and what do you with them all?