Breakfast for me is usually a liquid one and taken real early when its still pitch dark before I leave home: a mixture of 2% fat milk, total milk (casein & whey) protein powder, lecithin powder, flaxseed oil and maybe some spirulina powder and alpha lipoic acid! Keeps me going all day and one does not have to take time off fishing to eat. During the day liquids (water, mineral water and fruit juice) replenish lost fluids.

For you guys in the USA, a meal replacement powder such as EAS Myoplex mixed with 2% or skim milk would probably be more convenient and taste good too! Feeds the muscles so you can fish big swimbaits all day and still be ready to really "cross the eyes" of that monster when it inhales your lure!