The kendo menu cannot do it directly but you can use the change method of a data source and create the menu from this function, try this:
var menuDataSource = new kendo.data.DataSource({
                      transport: {
                            read: {
                              url: "/app/test/menuItems",
                              dataType: "json"
                            }
                          },
                        change: function() {
                            var dataMenu = this.data(); 
                            console.log("from change: " + dataMenu.length);
                            for (var indexMenuDataSource = 0; indexMenuDataSource < dataMenu.length; indexMenuDataSource++) {
                                var objectToPut = {};
                                var data = dataMenu[indexMenuDataSource];
                                objectToPut.text = data.text;
                                objectToPut.url = data.url;
                                objectToPut.cssClass = data.cssClass;
                                objectToPut.imageUrl = data.imageUrl;
                                if(data.items.length > 0){
                                    objectToPut.items = [];
                                    for(var indexSubItem = 0; indexSubItem < data.items.length; indexSubItem++){
                                        var subItem = {};
                                        subItem.text = data.text;
                                        subItem.url = data.url;
                                        subItem.cssClass = data.cssClass;
                                        subItem.imageUrl = data.imageUrl;
                                        objectToPut.items.push(subItem);                                            
                                    }
                                }
                                menu.insertAfter(objectToPut,  menu.element.children("li:last"));
                            }
                        }
            });
            var menu = $("#menuTest").kendoMenu().data("kendoMenu");
            menuDataSource.read(); //Will launch the change function
Note:  It is a draft, create another function to iterate over sub > sub > sub items.