When I eat, I generally take a break from gaming. I'll eat at my computer if I'm reading/watching something though. I drink water. I have two one litre bottles of water that I rotate, one if the fridge to keep cool and one with me to drink. I actually stopped crinking soda a few years back. I drink one every so often, but as a whole, I've stopped.
Just a bit of advice if you decide to stop drinking soda...don't stop cold turkey, especially if you're drinking a lot of soda. XD
On the few occasions I do eat when I'm gaming though, it's generally something quick that I can reach in real quick and grab a mouthful. Wasabi peas are good, saltines, flavored pretzels, and, on rare occasion, straight chocolate chips. XD