Magento 2.1 Sidebar – How to Disable Sidebar for Certain Category

Try bellow code on product listing block or list.phtml

public function currentCategory()    
{
    // Put here your current category id 
    $currentCategoryId = 3;
    $category =  Mage::getModel('catalog/category')->load($currentCategoryId);

    //OR $category = Mage::registry('current_category');

    $this->lastLevelCategory($category,2);
}
public function lastLevelCategory($category, $level=0)
{
    $html = '';
    $collection = Mage::getResourceModel('catalog/category_collection');
    $collection->addAttributeToSelect('url_key')
        ->addAttributeToSelect('name')
        ->addAttributeToSelect('all_children')
        ->addAttributeToFilter('is_active', 1);

    $collection->setLoadProductCount(true);
    $children = $collection->addIdFilter($category->getChildren());

    if ($children) {
        foreach ($children as $i => $child) {
            $this->lastLevelCategory($child, $level+1);
        }
        if(!$category->getChildren()) {
            $html .= "Category Name : ".$category->getName().'<br>';
            $html .= "Product Count : ".$category->getProductCount().'<br>';
        }
    }
    echo $html;
}

You can remove it by overriding the following template

/vendor/magento/module-catalog/view/frontend/templates/product/list/toolbar.phtml

and comment out the following code

   <?php if ($block->isExpanded()): ?>
            <?php include ($block->getTemplateFile('Magento_Catalog::product/list/toolbar/sorter.phtml')) ?>
   <?php endif; ?>

This will affect all categories.

To do it for a specific category. Create in your theme a custom_toolbar.phtml file like the original but with commented out the above code. Then go to the specific category in Magento admin, click on the tab Design and on the Layout Update XML add the following code

<referenceBlock name='product_list_toolbar'>
    <action method='setTemplate'>
        <argument name='template' xsi:type='string'>Magento_Catalog::product/list/custom_toolbar.phtml</argument>
    </action>
</referenceBlock>