An occasional treat is something that is enjoyed on a limited or infrequent basis. It's not something that someone would regularly indulge in, but rather it's a special and rare occurrence when they allow themselves to enjoy it. The term can refer to anything from food or drink to other activities such as going to the movies or taking a day trip. Essentially, an occasional treat is a small reward for something done well or simply a way to indulge in something pleasurable without overdoing it.