Solved it with this:
<?php if(get_field('faqs')): while(has_sub_field('faqs')):
$variable = get_sub_field('category');
if(get_sub_field('qa')): while(has_sub_field('qa')): ?>
<article class="envor-sorting-item <?php echo $variable; ?>">
<header><?php the_sub_field('question'); ?> <i class="fa fa-plus"></i></header>
<?php the_sub_field('answer'); ?>
</article>
<?php endwhile; endif;
endwhile; endif; ?>
Not sure what I was doing wrong before!! Hopefully it helps someone else
