Spike made a rueful smile.  "Well, like you say, normally the situation would be pretty erotic.  But assuming you want to keep it just friends..."  He makes a little laugh.  "I'll make a cut in my wrist, and you can drink from there.  It'll just take a few swallows, and the healing is almost instant.  The side effects...those last a few hours.  Your sight, sense of smell, and sensitivity to touch will be intensely more acute than you're used to.  Afterwards you won't have to wonder why vamps always get portrayed as sex fiends.  You can't help but be horny when you experience everything that intensely."