The rice cakes are a classic, I make a vegan version with tempeh and scrambled tofu - they are a great alternative to all the sweet on-bike food. However, this time of year all my riding happens early in the morning, and I find that the savory taste is not the best for first thing in the morning for me.
I am also a huge fan of the Rice/oat/dark chocolate/sea salt bites. They are super easy to make (mix oats and rice, throw in rice cooker; when cooked, mix with other ingredients, use their ice cube tray method for wrapping the bites) and easy to eat on the bike, even when I am having my breakfast on the rollers.