What about things like carrot and zucchini slice, or mini quiches?
My kids don't eat anything other than spreads in their sandwiches, so I usually send along a little box with a slice of ham or turkey, and some sliced up cucumber, capsicum, tomatoes, carrot, olives etc. to go with their Vegemite sandwich.
They will often get rice crackers and a piece of cheese (DD2 only gets the crackers, she doesn't dig on cheese) for morning tea, or air popped popcorn.
As far as baking goes, you could go for yeast based rather than cakey stuff. I find they lend themselves better to less sugary recipes. Things like vegemite scrolls, cheese and bacon rolls (my kids LOVE these) or home made crumpets. This is probably my personal bias though, because DD2 doesn't really like cake. I know, she's a weirdo.