Typically your average sugar vandal won't put enough sugar in the tank to make much of a difference. Now if you get a determined sort of fellow, who pours a 5 pound bag into your tank, then you most assuredly will experience some degree of problems. In real large quantities, sugar will simply fill the tank well from which the pump draws in the fuel. The vehicle will start, idle for a bit, then die.
If all of your vehicle's fuel filters are intact and functioning, then sugar in the tank will only prove to be a minor annoyance. You drop and flush the tank and lines, replace the filters, fill her up, and you are on your way. Hopefully you'll be on your way to your nearest auto parts vendor to purchase a nice locking gas cap.
In a former life I worked for a Honda dealership, and from time-to-time we saw this issue. It never resulted in engine damage. Granted, it is possible, but it's usually not the case. I can remember several times dropping the tank on a car for a completely unrelated issue, and finding some quantity of sugar/sand in the tank. With the owner of the vehicle having been unaware that it was even in there.
Bryan Carter