Free 500ml bottle of water with M&S sandwich and crisps: M&S instore
I think the cheapest sandwich is just over £1 for a pack of cheese and onion sandwiches, so a free 500ml bottle of still or sparkling water is a good deal for me.
Sorry my mistake, need to also buy crisps so is around a total price of £1.60.
Join M&S Sparks loyalty scheme for free. You earn "Sparks" as you shop which turn into rewards. Plus, in the past, members have received emails giving £5 off shopping; early access to sales; and invitations to special events.