History
Sandwich was the name Peter Parker gave to a stray dog he found on the streets while patrolling the city as Spider-Man. He gained its trust by giving it a sandwich he found in a dumpster, hence the dog's name.

Spider-Man swinging home with Sandwich
Peter tried to keep Sandwich hidden at his Aunt May's house. However, she quickly found out about Sandwich and called animal control, arguing they couldn't keep a dog, much to Peter's disgruntlement. The dog was eventually taken away.[1]