Eh, short term it’s no big deal. Teeth are durable as hell and won’t get fucked up by anything that minor if it’s a rare thing. But, the more you do it, the more damage accumulates over time. A few times a year over decades? Never gonna notice it.

A few times a month, and it’ll be a decade or two before it would be a problem.

A few times a week, and you’d better have dental coverage and/or good income, because you’re looking at a few years before it starts showing up as carries. Less if circumstances are bad, or you didn’t start out with very good teeth.

There’s also the fact that keeping in the habit of brushing after eating stays a habit better if you don’t deviate from it without an important reason. In my mind, if you’re awake enough to eat, you’re awake enough to brush afterward. If you aren’t awake enough to brush, then you probably shouldn’t be eating either. Fucks with digestion and metabolism. It’s better to just stay on track and skip the snack, if you dig me.

But nah, if it’s a rare thing, you’ll take more damage from a soda than a single night skipping brushing after a midnight nosh. It’s all about the acids.

Now, if you can’t be bothered to at least swish out with some water, I’d say you’ve got worse things to worry about because you can do that on your way back to bed, swallow it and take zero extra effort beyond the mouthful of water. If your energy is that low, or there’s some other impediment involved, focus on that.