One of the best things I swapped at the last Craft 2.0 was these sandwich wraps (pictured) that have saved me, Tom and the planet metres of Gladwrap.
Essentially, you make your sandwich, stick it in the middle of the unfolded wrap and then wrap it up, securing it with a velcro strap. They’re made of oil cloth so wipe clean and fold down flat in your bag once lunch is over.
I can’t say enough about how great these are. There are heaps of patterns, they’re New Zealand made and you can get yours online from this shop.