I have been making hats out of sweatshirt sleeves recently, and I wanted to share the results of my experimentation with you. I have found sweatshirt sleeve hats to be on the tighter side. The advantages of this are that it makes for a more airtight hat. Knit hats often let in some draft, but when I use a sweatshirt hat as an inner liner, I get the best of both worlds. I have only encountered two minor drawbacks so far. I prefer to either use a baggier sleeve to make the hat slightly on the loose side to avoid a hat that is too tight, allowing for the possibility of headaches as well as stressing my hair. (I guess most guys can disregard the latter if they are not growing out their hair.)
Here is a photo of the completed project:

Without further ado, here is the link to my published article on how to make a hat out of a sweatshirt sleeve.
Link to hat article