I've had those OEM mesh sun visors for the side rear windows on my X3 and was very satisfied with them. Takes all of 10sec per side to put on or remove, are very effective, and unlike tint, they work with the windows down too.
Didn't feel the need to get them for the E90, but I would not hesitate to buy them if I did.
2009 E90 M3 ED
2014 X1 28i ED