Question

I’m using the following code to pull random post data onto the sidebar of my blog. How would I add an image pulled from that post’s custom field “athletethumbnail”?
:

<?php
global $wp_query;
$current_id = $wp_query->get_queried_object_id();

    $my_query = new WP_Query( array(
        'post_type'=>'athletes',
        'posts_per_page'=>'1',
        'category' => '36' ,
        'orderby' =>'rand'
        ));

        if( $my_query->have_posts() ) {
        while ($my_query->have_posts()) : $my_query->the_post();

?>
<?php the_title(); ?>

<?php
endwhile;
}

wp_reset_query();
?>

Answer 1

From the docs found here, Under PostMeta Functions

These functions are intended for use inside The Loop, and all return arrays.

get_post_custom()
Get all key/value data for the current post.
................

Solution : You should use get_post_custom().

try this :

$custom = get_post_custom(the_ID());
echo $athletethumbnail = $custom["athletethumbnail"][0];

note: You should also be able to get away without passing the POST ID, as get_post_custom calls get_the_id id post id is not passed. source here

After changes :

    <?php
    global $wp_query;
    $current_id = $wp_query->get_queried_object_id();

        $my_query = new WP_Query( array(
            'post_type'=>'athletes',
            'posts_per_page'=>'1',
            'category' => '36' ,
            'orderby' =>'rand'
            ));

            // The Loop
while ( $the_query->have_posts() ) : $the_query->the_post(); ?>

<?php 
 $custom = get_post_custom(the_ID());
 echo $athletethumbnail = $custom["athletethumbnail"][0];
 the_title(); ?>

<?php
      endwhile;

// Reset Post Data
wp_reset_postdata();

?>