The caption for this photo should be, "I'm doing my best." No matter how hard I try to tuck, fold, smooth, rearrange, I can't quite get my sports bras to be picture perfect the way Queen Marie can. Alas, though semi-wrinkled and contorted, I'm quite pleased with how I can see all the colours and options easily, so I don't forget about any of my styles!
The method here is to lay your sports bra flat, fold the straps down the back (so you can tuck them away), then fold the bra in half. Again, you'll want to stand them up vertically so you can see everything, as you would in a file cabinet. It's easier than it sounds, despite the photo indicating an intense struggle.