South Yorkshire Police said a number of reports have been received, with mobility scooters among the items most commonly stolen.
Eamonn Larkin, a crime reduction officer, said: "Thieves are stealing various types of property but appear to be targeting mobility scooters, pedal cycles and food and drink.
"Please look at the security of your shed and if necessary, upgrade the security.
"Change the screws on the hinges to either clutch head screws, non-return screws or coach bolts. Reinforce the area around the lock with either marine quality ply or sheet steel.
"Consider purchasing a steel cable and anchor it to the floor and thread it around and through the articles in your shed, linking them all together. Secure the cable with a quality padlock. This will reduce the chances of a thief stealing your property.
"Don't help the thief by having a light in your shed. If you don't go into the shed at night, why do you need a light? Sheds are not designed or intended to be somewhere suitable to store valuable items, if the property is valuable keep it in your house."