If there's any food that a worm prefers, it's junk food. Wormate.io is proof enough of this. By eating loads of candy, these worms are able to grow to ridiculous lengths. The goal here is to become the biggest worm on the block, and the best way to go about that is to eat up the second-hand junk food gathered from the corpse of a much less fortunate worm.
Steer the worm with the mouse button, and avoid steering yourself into the body of another worm. That's how you die - instantly.
Take advantage of the power-up potions littered about the map. They do everything from allowing you to move 50% faster to gathering junk food from a larger distance.
Don't hesitate to be a bottom-feeder. You'll never be able to kill a worm 1000x larger than you, but that doesn't mean that you can't eat the super-charged junkfood that it will drop when it dies. So just stick near the big boys, and you'll be a worm for the history books in no time.