Hi, sorry to hear poor scooter is like this.
Like bunnies, piggies need to keep food moving through their gut to stay healthy, unlike bunnies, but like us, piggies cannot make their own vitamin c , but need it in their diet. So its important to keep food going through, and if possible, something with vitamin c. Wet dark leafy veg or herbs such as parsley and coriander/cilantro are good, but only if they are something he is used to, introducing new foods to a poorly bun or pig isn’t generally ideal. Having said that, he does need calories, a small, ie a dessert spoon, of porridge oats might be worth trying, if you have some in the house? they are easy to eat and high in calories. Another good food to feed a poorly pig is any part of a dandelion, the flower, stalk and leaves are all good. If he wont eat anything. then try feeding critical care, your vet might have some in? is he drinking and peeing OK?