Yes you can. Our bar area serves evening meals from 4pm to 9pm and we also have a 24hr Pizza and Jackets menu.
You are located in the terminal, so not only does the hotel have a snackish type service (e.g. pizza), there are also an array of restaurants in and around both terminals (you do not even have to leave the Gatwick complex) and serving all manner of food and booze. If it is only something light you want, there are no end of places to get sarnies, wine, fruit, etc. to pick up and take out.
Get an answer from Hampton by Hilton London Gatwick Airport staff and past guests.