As we know from a previous post the "sloth and torpor" hinderance can fully mean: Lethargy and drowsiness: Lacking driving power, lethargy, not having vigor or lacking energy, unwieldiness, laziness, sleepiness, drowsiness, dullness of the mind.
In chapter 146. Getting Rid of Drowsiness (VII 58A) of the Numerical Discourses of the Buddha, the text suggests 8 ways to cope with drowsiness. This isn't just for meditation, it's probably if you're also reflecting or even communing with sangha, perhaps anything you do.
1. Do not give attention to a thought that leads to drowsiness. For instance if I think about all the things I have to do, I get drowsy sometimes. Or perhaps a particularly hard issue. Now meditation is not thinking and not not thinking. You have an object of focus or even no object of focus, and when thoughts come up you usually just let them pass by. But still there are thoughts that will lead to drowsiness and you can just not pick up those thoughts. I suppose these countermeasures can also be for reflection, you could be reflecting and this hinderance can come up.
2. You can think about the Dharma, what you have learned and mastered. Perhaps if you're drowsy you've lost the flow of where you are heading, your vector, your aspirations. If you think about the Dharma and why you're even doing this. Motivation is important to get you though the tough times, the dark night of the soul, and through drowsiness. This should be personal and I'm just going to riff now about what I could think about.