How can I avoid feeling ill on the eurostar?

Most people do not feel ill on Eurostar trains. As long as you are not travel sick on trains, you should be OK.

If you do feel travel sick on trains, the best advice is not eat a lot of food before riding the train, close your eyes often, do not read or watch television, and if you want to open your eyes, look at distant non-moving objects like trees and grassland.