Spike's never really considered blokes as an option until recently, partially because he was so consumed by Dru for so long but mostly because it just wasn't his thing, regardless of what Jack thinks. After a century, you have a pretty good idea of what you're into. Still, he has to admit that there are a few perks to being with the stupider sex. The firm feeling of arousal pressing against him for one, so noticeable and difficult to ignore, not that he has any plans on ignoring it this time.
He pulls back after a moment, sitting up to give Jack a chance to breathe and himself a chance to deposit the bottle off the side of the bed and wrestle out of his t-shirt. Looking down at Jack with a shit-eating grin, he rolls his hips again with purpose.