Eating food on the bike is essential for top performance. It is just as important as staying hydrated on long rides.
It always helps to bring food that you think is good, that you will want to eat at any point. You can't have some crazy unappetizing "healthy food." You need something yummy!
However, this logic does not apply to everything. The guys from GCN take us through the top 10 things not to eat while cycling!