There is a pizzeria called Marianno located in the center of Sobrance. Visitors can park in the owner's parking yard with permission. The restaurant offers delicious pizza and provides amenities such as water, electricity, sewer, and waste bins. The owner, Marian, is friendly but doesn't speak English. He can offer travel advice in Slovak to those who can understand.
Don't expect a warm welcome, even if you're their customer. I didn't have the courage to ask for their customer bathroom to empty my toilet cassette, even if I offered to pay. They probably would have provided services, but I heard them laughing among themselves. So I just spent the night in that open parking lot accessible to anyone.