Start by cutting a circle around the stem of a large or medium sized pumpkin. Use a pumpkin carving knife for this purpose. Make sure that circle of your cut is large enough for you to reach inside the pumpkin with your hand.
Take out handfuls of the contents found inside the pumpkin and place them in a bowl. Do not make the mistake of throwing away the insides because you will need them later on. Make the pumpkin hollow as much as possible and set away the bowl you were filling for the time being.
With a marker, draw the face on the now hollow pumpkin. Try to make the mouth fairly wide. This will be useful to replicate the puking effect. You may want to look at pictures of puking Halloween pumpkins made by others. Such pictures are easily available on the internet.
Keeping your focus on replicating the puking effect, carve the face out with a pumpkin carving knife. Make sure that the blades of the knife are sharp in order to get a clean finish. It would be better to keep the eyes of the pumpkin relatively simple to that emphasis can be focused on the puking effect.
Carefully place the pumpkin at the desired location. Take the bowl that contains the pumpkin’s insides. Place the insides in such a way that they look to be coming out of the mouth of the pumpkin to make the pumpkin look like as if it was puking. Make sure that you keep the insides connected.
Finally, to make the pumpkin puke look real, add different items such as pieces of candy corn or even paper clips. It would seem as if the pumpkin has eaten those things and was now puking them out. To finish the task, place a candle in the middle of the pumpkin and light the candle.