I remember watching an interesting investigative documentary on the sports industry in general. This covered food, drink, and footwear amongst other things. They came to the conclusion that with few exceptions, it was all just a big con to get you to spend lots of money on stuff you don't really need.
For the purpose of this post, one of the most interesting, and amusing, sections, was when they spoke to Graham Obree, the Scottish cycling legend who built a track cycle in his kitchen, out of, amongst other things, bits from an old washing machine. When out training, he took water to drink, and jam sandwiches (on brown bread), which, he insisted, was gave him all he needed!.
Personally, i cant go without breakfast, this consists of 2 cups of either Earl Grey, or redbush tea along with, in the winter, porridge, and in the summer, a mixture of muesli and granola with some seeds and nuts mixed in. This keeps me going fine till dinner, and, like breakfast, i cant miss my dinner (though i may only stop for as little as 20 mins).