"Spike," he says patiently, "I don't eat."

"I don't see why the hell not."

"I'm a vampire.  There wouldn't be much point."

"It's fun!  It tastes good!  That's the FUN!!!"  I peek into the refrigerator.  I need pretzels.  You can't get plastered without eating pretzels.  It's a rule.  Well, it's *my* rule, anyway.  "You do remember fun, don't you, Peaches?"  I peer into desolate, chilly shelves.  Six bags of blood and a bag of ice. "You certainly don't remember pretzels, at any rate."

Donna and others, "Days of Our Unlives"

Most vampires don't seem to have a lot of vices outside blood- why so many for Spike?  It could suggest a lingering sense of humanity, or simply a tendency to become bored.  There's a certain hedonism about his character; if it's not fun, he doesn't bother.  Here's a list of things that Spike looks towards to keep himself amused.

>>alcohol
>>smoking
>>food
>>drugs
>>music
>>tv
>>decorating