I love these shirts for the gym! I hate wearing cotton shirts to work out because I don't like it when they show sweat stains, but these shirts are super comfy and breathable and don't show any sweat.
That said, even after washing them twice with hot water, they still smell a bit like sweat. These are the only shirts I have this issue with, so it seems the material just absorbs the smell of sweat more than others, so just beware of that.