var app = angular.module('plunker', ['ui.bootstrap']);

app.controller('MainCtrl', function($scope) {
    $scope.name = 'World';
});

app.controller('DropdownCtrl', function($scope) {
 
    $scope.items = [
        "The first choice!",
        "And another choice for you.",
        "but wait! A third!"
    ];
});
<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>

    <link data-require="bootstrap-css@*" data-semver="3.0.0" rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" />

    <script>document.write('<base href="' + document.location + '" />');</script>
    <script data-require="angular.js@1.1.x" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.1.5/angular.js" data-semver="1.1.5"></script>
    <script data-require="ui-bootstrap@0.5.0" data-semver="0.5.0" src="http://angular-ui.github.io/bootstrap/ui-bootstrap-tpls-0.6.0.js"></script>
    <script src="app.js"></script>
    <style>
    .dropdown-menu .sub-menu {
        left: 100%;
        position: absolute;
        top: 0;
        visibility: hidden;
        margin-top: -1px;
    }
    
    .dropdown-menu li:hover > .sub-menu {
        visibility: visible;
        display: block;
    }
    </style>
  </head>

  <body ng-controller="MainCtrl">
  
    <nav class="navbar navbar-default" role="navigation">
      <!-- Brand and toggle get grouped for better mobile display -->
      <div class="navbar-header">

        <button type="button" class="navbar-toggle" ng-init="navCollapsed = true" ng-click="navCollapsed = !navCollapsed">
          <span class="sr-only">Toggle navigation</span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
          <span class="icon-bar"></span>
        </button>
        <a class="navbar-brand" href="#">Brand</a>
      </div>
    
      <!-- Collect the nav links, forms, and other content for toggling -->
      <div class="collapse navbar-collapse" ng-class="!navCollapsed && 'in'">
      
        <ul class="nav navbar-nav">
          <li class="active"><a href="#">Link</a></li>
          <li><a href="#">Link</a></li>
          
          <li class="dropdown">
            <a href="#" class="dropdown-toggle" ng-controller="DropdownCtrl">Dropdown <b class="caret"></b></a>
            <ul class="dropdown-menu">
              <li>
                <a href="#">Sub menu &raquo;</a>
                <ul class="sub-menu dropdown-menu">
                  <li>
                    <a>Second Level &raquo;</a>
                    <ul class="sub-menu dropdown-menu">
                      <li>
                        <a>Third Level &raquo;</a>
                        <ul class="sub-menu dropdown-menu">
                          <li>
                            <a>4th Level</a>
                          </li>
                        </ul>
                      </li>
                    </ul>
                  </li>
                </ul>
              </li>
              <li><a href="#">Another action</a></li>
              <li><a href="#">Something else here</a></li>
              <li><a href="#">Separated link</a></li>
              <li><a href="#">One more separated link</a></li>
            </ul>
          </li>
          
        </ul>
        <form class="navbar-form navbar-left" role="search">
          <div class="form-group">
            <input type="text" class="form-control" placeholder="Search">
          </div>
          <button type="submit" class="btn btn-default">Submit</button>
        </form>
        <ul class="nav navbar-nav navbar-right">
          <li><a href="#">Link</a></li>
          <li class="dropdown">
            <a href="#" class="dropdown-toggle" data-toggle="dropdown">Dropdown <b class="caret"></b></a>
            <ul class="dropdown-menu">
              <li><a href="#">Action</a></li>
              <li><a href="#">Another action</a></li>
              <li><a href="#">Something else here</a></li>
              <li><a href="#">Separated link</a></li>
            </ul>
          </li>
        </ul>
      </div><!-- /.navbar-collapse -->
    </nav>
    
    <div class="container">
      <p>Hello {{name}}!</p>
      
      <div class="btn-group">
        <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
          Dropdown <span class="caret"></span>
        </button>
        <ul class="dropdown-menu" role="menu">
          <li>
            <a href="#">Sub menu &raquo;</a>
            <ul class="sub-menu dropdown-menu">
              <li>
                <a>Second Level &raquo;</a>
                <ul class="sub-menu dropdown-menu">
                  <li>
                    <a>Third Level &raquo;</a>
                    <ul class="sub-menu dropdown-menu">
                      <li>
                        <a>4th Level</a>
                      </li>
                    </ul>
                  </li>
                </ul>
              </li>
            </ul>
          </li>
          <li><a href="#">Another action</a></li>
          <li><a href="#">Something else here</a></li>
          <li class="divider"></li>
          <li><a href="#">Separated link</a></li>
        </ul>
      </div>
    </div>
  </body>
</html>