How can I add an ID to the Body tag?

In Oxygen I can do this…

add_action('oxygen_vsb_body_attr','my_body_id');
function my_body_id() { 
	echo ' id="my-site" ';
}

Does Bricks have a similar hook for the Body tag?

You can try this

add_filter('bricks/header/attributes','my_body_id');
function my_body_id( $attributes ) { 
	$attributes['id'] = "my-site";

       return $attributes;
}

Thank you! The filter needed is actually ‘bricks/body/attributes’, and it works exactly as expected.