Tool batteries are different from laptop batteries for example, because they need to support really high discharge rates in bursts. An angle grinder or a circular saw can draw dozens of amps at 20V or thereabouts.
So these batteries are made with very thick copper and aluminum foil electrodes. A nice "free feature" here is that you can charge them at very high rates, because there is almost no resistance between the terminals and the electrochemically active part of the cell.
They do not get that many cycles. A few hundred typically. If you get the good stuff.
I would not consistently use them for lighting, because it is really expensive per watt-hour.
@Danjo: one very interesting learning is that you can get away with a lot less light than you think you need. With one watt of LED lights, you can manage perfectly fine in a bus. It's not as bright as at home, but it doesn't need to be. It seems like a big compromise, but it's not.
If I would go for the cheapest viable option, I would buy this:
https://www.amazon.com/Nekteck-Water...8866588&sr=8-5
A pack of these:
https://www.amazon.com/Flexible-Lapt...NsaWNrPXRydWU=
Assuming they have USB power banks laying around.
These are cool but... way too much light!
https://www.amazon.com/Onite-20-US24...s%2C468&sr=8-2