Answer by Clayton C. Anderson, Former resident of the ISS for 152 days in 2007, 12 days in 2010:
Oh man! Here we go!
THIS astronaut wore Hanes brand, perfectly white cotton (at least they started out that way!), loose-fitting boxer shorts... every single day. And each of those days was spent on board the International Space Station (ISS) over the summer of 2007.
The difficult part was that I had to wear those boxer shorts for at least four days. You see, with no laundry service up there, clothes (including underwear) are what we at NASA call a "consumable." Using up your consumables too fast results in a need for more frequent supply deliveries, and when those deliveries come by rocket ship... well, let's just say it's a bit costly.
Never one to be cavalier with taxpayer dollars, I made the best possible use of my briefs. After four days, I turned them inside out... four more days. Then, I rotated them 180 degrees and yep ... four more days. Most of you can see where this is going, so I turned them right side out and again... four more days! If you believe all that, then I have some swamp land in Florida ready for your purchase.
While not being worn according to NASA procedures, donning a clean pair of boxer shorts was always an uplifting experience!
My Russian colleagues -- much to my surprise -- wore American style "tighty whities" (also Hanes) during our five-month stay. NO ON ... that's right, no one, wore the Russian-supplied male briefs during our stay together in space. Looking much like a European Speedo, they simply didn't provide #TheOrdinarySpaceman with ample coverage, and they crept up on me... even in zero gravity! So, as a matter of practicality and conservation of resources, I used them for packing material. In one instance, I signed a pair with a Sharpie and sent them home wrapped around a science payload, much like a shipping company uses foam peanuts. Imagine the expressions on the faces of the folks who unpacked that cargo transfer bag!
During my second flight, on the space shuttle Discovery mission STS-131 in 2010, I was asked by the lovely ladies who assembled our crew clothing of my underwear preference. This time, I requested they surprise me, with a specific caveat telling them "no loosey goosey white boxer shorts." The result was wonderful! Red, white, and blue horizontally-striped Hanes Michael Jordan extended-leg cotton briefs. Beautiful! You can find a pair of them hanging on the wall of a very famous steakhouse in Phoenix, AZ.
Keep lookin' up!