If category then echo a custom fields

Use the in_category() function, like this:

<?php if ( in_category( 4 ) ) : ?>
    <div class="event-post-icons">
        <ul>
            <li class="single-post-date"><?php the_field('event_date'); ?></li>
            <li class="single-post-time"><?php the_field('event_time'); ?></li>
            <li class="single-post-price"><?php the_field('booking_fee'); ?></li>
            <li class="single-post-palce"><?php the_field('event_location'); ?></li>
        </ul>
    </div><!-- /event-post-icons -->
<?php endif; ?>

If you are using this to test a post outside of The Loop, you would need to add the post id:

<?php if ( in_category( 4, $post_id ) ) : ?>