After politics, religion and sex it should be sport.
Whilst gaming, I like non-messy food I can eat with one hand and put down easily, so I can play games and eat at the same time without splattering gunk and crumbs on my computer.
Drinkwise, for a strategy game, you want something to savour, to take your time on and let the taste roll around your mouth, add to your contemplative state. Good wine or spirits. For more action-orientated games, you want a drink you can bombastically chug down in a few spare grabbed seconds before the next wave of high-octane activity. Beer, maybe cheap plonk.
Music should be appropriate to the game. The first issue is pace: listening to something mellow whilst charging around a first-person shooter just doesn't work. The other thing is the general atmosphere. I have the Conan the Barbarian soundtrack (!), which goes quite well with Dominions. The SF-themed "Pocket Universe" by Yello went very well with Starcraft, they came out about the same time.