The only place I have heard of that charges a split fee in the parks is Blue Bayou.
Other than that, any counter service obviously is super easy to split. I like to share the french dip or stew in a breadbowl at the French Market, the chicken fusilli at Pizza Port and the steak nachos at Whitewater Snacks.
I've actually shared a kids' meal (chicken strips or grilled cheese) at WWS with my dd who is a very light eater. I just supplemented with a side salad. We were able to share the refillable kids' drink and I filled my water bottle at the soda station with cold filtered water. That meal cost us $8.