I badly need to get my endurance up, especially since baseball season is about a week away. I can barely run 20 minutes on the treadmill, so thats a sign to me that I need to get my stamina up. What aerobic excercies can I do and is there any food I should eat and shouldent eat?

Baseball is not a game where aerobic endurance is needed. Anaerobic endurance is another story. Vast amounts of cardio work will hinder a baseball players potential in the long run. You need to work on being able to turn on your power and leave it on for short bursts of time, over and over again that is anaerobic endurance. Baseball is a power sport and a player should train that way.

Soooo what your saying is I should lift weights and do sprints?

Plyometrics are another way to train anaerobically in addition to lifting and sprints.