This might be something you may have to experiment with. Unlike Geonz, I cannot do my morning ride on anything more than a glass of something wet and maybe a piece of toast, otherwise I feel like I am going to hork it all over the road. But I haul my food items for the day with me anyway and will graze once I get settled in at my desk. I make sure that when I get to work, to have some carbs and a bit of protien. Sometimes this is a bit of chocolate milk, other times, bagle, fruit and a piece of string cheese. I have a 19 km commute each way and with traffic lights and all, it takes about an hour each way. I found it helpful to drink en route and to make sure to hydrate through the day. I get tired and headache-y if I don't.
Four wheels move the body, two wheels move the soul.
2010 Kelson custom/Brooks B17 Imperial
2009 Masi/Terry Damselfly
2004 Specialized Dulce Elite/Terry Damselfly
2003 Gary Fisher Tassajara/unknown saddle
1987 Bridgestone 100/Terry Liberator X