I have to admit .. having fixed more then one car with sugar in the tank.. yes it does it's damage.. the sugar gets pilvarized by the sloshing of fuel and can break down or even melt when the fuel pump heats up.. sugar has a low melting point. so i have changed MAP's..injectors.. chipped out intakes and flushed many a fuel line with hot boiling water.. also .. just an FYI the worst damage is done in an area that has climate changes or is colder more then it is hot.. the colder weather helps the melted sugar harden like rock candy till t builds up.. and clogs vacums and injectors.. it can be very costly and the reason a sugared engine goes BOOM!! is the clogging damage runs the motor lean and well we all know what that does,..