I have a bunch of sweatshirts that are too large now. How to reuse?

Donate them. Make a rag rug or quilt. Sew panels together and bring them to an animal shelter.

Cut the arms off and make leg warmers, use the body to upholster pillows, if material is tubular..no side seams, they can be stuffed for washable pet beds, use two, three cut intoa single piece of material, stuff then sew up sideseams, cut into squares, make into 12" x12" squares, or what ever size you like, make a quilt...throw for snuggling...

Donate or gain weight.

Depends what shape they're in, of course. I'm assuming that you've already gone through and discarded damaged ones and given others to Salvation Army, etc and now you're left with your favorites. So, a couple of thoughts. Cut up damaged ones for cleaning rags and patchwork pieces for lap throw. Nicer ones you could cut up middle and put buttons for diy cardigan. You could also cut junkets into strips and weave together for rugs, totes, placemats etc. Hope this gives you some ideas😃 Happy new year!

Cut the bottom off , the neck out and the end sleeves. Use cross stitch thread to sew around bottom , end of sleeves and neck and add anything you want to cross stitch or embrider on your sweat shirts , or add patches ...