Solved, for anyone browsing.
Passing the arrays in the index method of the controller like below did it for me.
$data['result'] = $this->team_m->get_team_by_coach();
$this->load->vars($data);
And in the sidebar view like so:
<ul id="menu" class="nav nav-pills nav-stacked">
<li><a href="<?php echo base_url(); ?>"><span class="glyphicon glyphicon-list"></span>My Teams</a></li>
<ul id="submenu" class="nav">
<?php foreach ($result as $row): ?>
<?php echo '<li><a href="http://localhost/master/index.php/team/' . $row['id'] . '">' . $row['teamname'] . '</a></li>';?>
<?php endforeach;
if(count($result) <= 2)
{
echo '<li><a data-toggle="modal" id="create_team" data-backdrop="true" href="#create_team_modal" href="base_url(index.php/team/create_team)"><span class="glyphicon glyphicon-plus"></span>Create a team</a></li>';
}
?>
</ul>
<li><a href="<?php echo base_url(); ?>index.php/message"><span class="glyphicon glyphicon-envelope"></span>Messages</a></li>
<li><a href="<?php echo base_url(); ?>index.php/profile"><span class="glyphicon glyphicon-user"></span></i>My Profile</a></li>
<li><a href="<?php echo base_url(); ?>index.php/auth/logout"><span class="glyphicon glyphicon-log-out"></span>Logout</a></li>