If your sponge cake has toppings, you need to take one additional step to ensure the toppings stay put.
Make sure your cake is totally cooled if you made it at home.
Portion it out in the amounts you will need at defrosting time.
Set your portions in a single layer on a cookie sheet and pop into the freezer to flash freeze. This should take an hour or so, just long enough for the toppings to be hard so they don't get smashed.
Remove from the freezer and wrap each portion in a layer of plastic wrap and/or aluminum foil.
Pop your wrapped portions into an airtight container or a freezer bag and close it up.Freezer bags: make sure you press any air out before closing it up. Take a marker and write the date on your package, then place it in the freezer.