Here are the things I would try:
2. Chemicalguys water spot remover
Make sure you use a good wax and/or and sealant to prevent this from happening again!
2006 E90 SG-Dinan Ram Air Intake-Dinan Throttle Body-Dinan Exhaust-19' Hyperblack CSL's-15/5 tint-Matte Black Grills-M3 Spoiler Lip-Amber Delete-Smoke Side Signals