There are a whole lot of things people often feed dogs but are actually quite bad for them.
I think in small quantities they can be ok - won't kill the dog - but if its a regular thing, can cause all sorts of problems.
It is a challenge explaining to my dog that she can't have date and walnut slice - cos of the walnuts, or anzac slice - cos of the raisins, and never mind the sugar that isn't great either.
We had one dog that ate quite a few grapes, sultanas and used to pick cherry tomatos off the bush and eat them... not good. She also managed to eat half a football of easter egg and chocolate truffles cos someone was dumb enough to hide their stash where she could find it. I'm sure she would have eaten all of it if she hadn't started upchucking everywhere... and given the game away. Probably saved her life. After that we got her some "dog chocolates" made out of carob. And occasionally used to trick guests into eating some of those. Carob bleah. Dog liked them.
Onions - especially raw onions are another no no. I won't cos the farts are unbelievable - paint stripper. But too much raw onion can kill a dog. Like 3 whole onions - but the amount can be less for smaller dogs.