Any significant amount of meat or anything with a lot of fat will be difficult to digest. So avoid those during rides.
I personally think that it's not healty to consume large amounts of sugar, except while riding. But I know people who do and ride ok. I avoid ice cream when I am trying to lose weight for climbing races but other than that there's no need to totally deprive oneself. A reasonable amount every once in a while is fine; a pint a day would be less than optimal.
Eating the "right" food (for you as everyone is different) won't make you faster, but eating the wrong food (for you) could make you ill during a long race or event.