Polyester fabric tends to hold the body odor even after washing, and in my opinion it might seem okay when you put it on fresh and dry but as soon as it gets a drop of new sweat it reactivates so you instantly smell like you've been sweating in it all day. It seems to vary by individual items, certain slick knits in particular I have had to toss out because I just couldn't get the smell to stay out. Other items are no problem. If you are wearing something for the purpose of working out and sweating, you're not trying to spark romance or seal a business deal, so being sweaty and stinky with honest effort isn't really a problem. You'll just get 'er done and then take a shower and change. If you're wearing sportswear to hang out, give it a sniff, and/or ask a person who's going to give you an honest answer. Don't ask "Do I stink?" Ask, "Does this shirt stink, should I change it?" Because it feels a lot less mean to say Yes to the second.

They are great for taking your sweat away from your body. The problem is they also get you skin oils as well, which is why the smell a lot more than cotton for example that only holds onto the water part of your sweat

Personally, I love merino wool t-shirts. Try one out, a summer one that is thin