I looked into printing sleeves but the problem was the minimum order was 54 cases. Same with cups. Not much more per cup but large minimums. I went with stickers. It doesn't take long to sticker a few sleeves of cups and there is always a little down time.
Maybe you didn't look far enough... we use a plain white cup w/ printed logo sleeve and we do NOT have 54 cases sitting around! I'm definitely a fan of stamping the sleeve; why bother putting any effort into a fancy cup when it's just going to get covered up with the sleeve