Keep multiple InfoWindows open when Marker is clicked in Google Maps

You have declared the InfoWindow globally and hence it closes when you open new and hence delcare it within the function

window.onload = function () {
var mapOptions = {
center: new google.maps.LatLng(markers[0].lat, markers[0].lng),
zoom: 6,
mapTypeId: google.maps.MapTypeId.ROADMAP
};
//var infoWindow = new google.maps.InfoWindow();
var map = new google.maps.Map(document.getElementById("dvMap"), mapOptions);
 
for (i = 0; i < markers.length; i++) {
var data = markers[i]
var myLatlng = new google.maps.LatLng(data.lat, data.lng);
var marker = new google.maps.Marker({
position: myLatlng,
map: map,
});
(function (marker, data) {
google.maps.event.addListener(marker, "mouseover", function (e) {
var infoWindow = new google.maps.InfoWindow();
infoWindow.setContent('Business Name:' + data.title + '<br/>Address:' + data.description + '');
infoWindow.open(map, marker);
});
 
})(marker, data);
}
}