Well in the 50s when I first started on long distance work driving for Baxters Road Services on Newcastle Quayside There was a Cockney lad worked there He was noted for going through drivers stuff in their cabs on a weekend, Stealing anything that he could get his hands on, Anyway I used to buy Beechnut chewing gum in those days & he used to steal it whenever he got the chance, So I bought some Bonamint Laxative peppermint chewing gum & replaced it in the Beechnut wrapper, Well It worked a treat he had the ■■■■■ for days & had a few days off too,But sadley it didnt stop his theiving habits, But it did end when he got the push for stealing fuel, 
, He claimed that he was born to the Bow Bell Chimes making him a true Londoner, But he said he was born in Cripplewood, Now I allways thought it was called Cricklewood, But having said this he was as thick as they come i my book, Regards Larry.
Removed. Reason: identifying names
Where I work there are only a handful of us and we all know each other. Your sat-nav, cash, wet wipes, air freshener or anything else can be left in your truck, it’ll still be there the next time you jump in.
Biscuits/sweets etc are a different matter, foraging for food is perfectly acceptable 
Supermarket work/big fleet with a multitude of drivers, leave nothing, it’ll disappear. Basic common sense tbh.
Leave some sweets in a tin in the cab but sprinkle some of that senokot laxative powder onto them and shake well to hide any residue. Granted the sweets will be nicked but the culprit will be off sick with an upset stomach.
Or cough and sneeze, scratch your arse and handle some food and leave in the cab for the thief to feast upon.