I have three vouchers for a free fruit and veg box, if anyone can use one.
You have to create an account with the site, but friends who have had previous vouchers have had no problem cancelling their account if they don't want to then pay for future boxes.
From memory, I think you have to be a new shopper with them to claim.
You also seem to have unlimited choice of boxes, so can order the biggest or the smallest.
Disclaimer: if you order a box, I usually get a small free item in my own order 