Try using a “counter” variable for the loop maybe?
<?php
if ( get_field('ingredients-list') )
{
echo '<ul class="ingredientsList">';
$count=0;
while ( has_sub_field('ingredients-list') )
{
echo '<li class="ingredient" itemprop="ingredients"> <label for="check-'. $count .'"> <input type="checkbox" class="check" id="check-'. $count .'"> ';
if ( get_sub_field('quantity') ) echo '<span class="quantity">' . get_sub_field('quantity') . '</span> ';
if ( get_sub_field('measurement') ) echo '<span class="measurement">' . get_sub_field('measurement') . '</span> ';
if ( get_sub_field('ingredient_name') ) echo '<span class="name">'. get_sub_field('ingredient_name') .'</span>';
if ( get_sub_field('measurement') ) echo '<span class="notes">' . get_sub_field('notes') . ' </span>';
echo '</label>';
echo '</li>';
$count++;
}
echo '</ul>';
}
?>