Do I need to wear a sport coat?
According to the website, yes, for both lunch and dinner in the restaurant (but no mention of that mandate in the bar):
https://www.sevenrooms.com/experiences/maximsparis/dinner-4558117570625536 (dinner)
https://www.sevenrooms.com/experiences/maximsparis/restaurant-6103058176294912 (lunch)
"Dress code:
Chic and elegant
Mandatory suit jacket for men."