No sugar from soda... I've drunk diet soda as long as I can remember. My belief is that anything with significant sugar in is highly addictive; I've got a very very addictive personality, and have never felt remotely addicted to soda, but have also only ever drunk diet soda.
To be fair, OP said 'sugar in the form of cakes, candy, and donuts'. Also, sodas are a special case, as they have pretty much zero nutritional value and, unlike solid food, do nothing to fill you up.