Removing Sharpie ink from a sticker or any surface made of plastic is easily done in a minute or less using dry erase markers and a rag or paper towel.
Use a dry erase marker
Carefully mark over the portions of the sticker that are marked by Sharpie ink with a dry erase marker.
Wipe the surface clean
Rub off the Sharpie ink markings together with the dry erase marker using a rag or paper towel.
Repeat the process to clean the surface completely
If not all Sharpie ink markings are removed the first time, repeat steps one and two until the whole sticker surface is clean.