It seems reasonable to provide kosher food, tefillin, sefarim, etc.
We can probably offer to keep him under control (to the extent that’s legal). Depending on the country, agreeing to house arrest (in yeshiva), and full cooperation with the police, might work in more developed countries.
We also should look into whether the kid is really guilty.
Exactly what is money needed for? Was the kid arrested in a country where bribery is the accepted method of dealing with the authorities? Is it for a local lawyer? Few countries offer cash bail, and in any event, if you skip bail you lose the money and become an international fugitive.
Would our response be different if the kid were caught shoplifting or selling contraband within our own community?