Although not the most beautiful beach in Mauritius, Flic-en-Flac is one of the most touristic city and offers many restaurants, bars, hotels, and shops. Street food and watersport activities vendors walk around all day long, willing to offer their services to locals as well as tourists.
The beach is wide, facilities such as showers and toilets are free and properly maintained, there are booths for picnics and barbecues, and on the weekends there are often free music and dance shows. However beware of drunk people wandering around at odd hours.
Try the beach side close to the hotels, then the main area close to the town entrance, and grab a bite there at Jeanno's Burger.