Charge motorcycle battery with power supply?

I want to run a BT speaker with a motorcycle battery (12v 5.0Ah) and I want to use something like a laptop charging plug.

And the question is whether it works? Or how to do it?

Either way, you should first learn the basics of electrical engineering for something like this.

Charger or voltage converter with 12V input and the corresponding output.

If the speaker is charged via USB cable, a USB adapter for the cigarette lighter does

Generally, yes. If you can monitor voltage and current manually:
2 measuring devices required.

And of course the power supply must deliver the correct voltage, i.e. At least 14 V DC.

Loading is gentle with no more than 10% of the capacity,

So 1.5 A for a 15Ah battery

the voltage then reaches 2.3 V per cell (i.e. 13.8 V for a 12 V battery)
Lead gel may also be 2.4 V, i.e. 14.4 V for the 12 V battery.

If you don't know your way around and just plug it in, the charger and battery could go on.

Purchased chargers regulate current and voltage so that the battery does not
Takes damage. And they did even more: "Intelligent" chargers also recognize defective batteries, and could use a special charging program to refresh older batteries a bit (but you shouldn't expect too much).

And you can safely clip them on for days. And there's something from 20 euro, if it does not have to be a high amperage for quick charging of large car batteries.

Lead-gel battery? There are reasonably useful chargers for around 20 euro.

Cheap standard: https://www.bueromarkt-ag.de/autobatterie-ladegeraet_dino-kraftpaket_6v12v-4a,p-136311,l-google-prd,pd-b2c.html

I also use a similar part, although it does not show the voltage exactly, but it works and loads as desired.

Since lead batteries are not normally installed in laptops, I would not use their chargers for lead either. I guess the charging voltages are too different, even if they are also built for 12V.

I would rather recommend an electronically controlled charger. For example: https://www.bueromarkt-ag.de/autobatterie-ladegeraet_dino-kraftpaket_6v12v-4a,p-136311,l-google-prd,pd-b2c.html This also protects the battery.