[Could he be convinced towards kitchen sex in a more general sense? Probably, though he wasn't thinking much in that direction, distracted more by the idea of a frosted cock. Without the use of inappropriate condiments, kitchen sex was just sex in a kitchen. When he knew they were capable of fucking anywhere given the right motivation, he didn't see anything in singling it out.

But he relents a little, when Mettaton seemed willing to drop the insistence on icing. He knew this was a vulnerable point. A sore point, even. If they were to do anything at all, they required something a bit slick, and the robot's lack of saliva production was a hindrance for anything involving his mouth. Even if they might manage without a slick supplementary, they would vastly benefit from its inclusion. And without anyone selling anything appropriate, they would have to find that supplement elsewhere.

Exhaling slowly, he fixes the other man with an even stare.]

Then, Mettaton- icing is a poor choice regardless, if the idea is for anything to feel better.

[And when he found it unappealing in its own right, at best something he could tolerate if not enjoy, when it didn't provide a practical function either- he turned against it entirely.

(Not that slathering anything food-related on him appealed. Nor in cleaning it off of Mettaton.)]

Nor do I need to watch you lick something else off, to know that you want something from me.