products_index.html

<div class="products cities-content">
  <ul class="unstyled cities-items" style="color:white;">
    <% sort_by_sold_out_or_ended(all_products_and_categories.sort_by(&:weighted_position)).each_with_index do|product_or_category, index| %>
     <%= render product_or_category %>
    <% end %>
  </ul>
</div>

sorting.rb

def all_products_and_categories
  categories.each_with_index do |category, index|
    product.insert((index*4), category)
  end.compact
  return product
end

class Category
 def sold_out
  false
end