Hi, both my boyfriend and I are vegan and have been for many years. I do shorter rides, closer to metric centuries, but he does lots of centuries and longer endurance events.
Our lifestyle/diet is about environmental issues more than health so we eat healthy but not always
Potato chips are still vegan and I make a lot of cookies. That said, plant based convenience foods are harder to find/more expensive than they're meat/dairy counterparts. So by default you end up cooking at home a lot which is much healthier anyway.
My favorite snacks on rides are luna bars, lara bars, primal strips, peanut butter sandwiches, and dates.
It's definitely possible to be an endurance athlete on a plant-based diet. Let me know if you have any specific questions.
2009 Surly Cross Check
2003 Cannondale Bad Boy
Motobecane Nobly (60's or 70's)