Show the infoWindow of the marker.
marker.showInfoWindow();
<div id="map_canvas"></div>
var div = document.getElementById("map_canvas");
var map = plugin.google.maps.Map.getMap(div);
var marker = map.addMarker({
'position': {
lat: 0,
lng: 0
},
'title': "Hello GoogleMap for Cordova!"
});
// Show the infoWindow
marker.showInfoWindow();