How do I cap the water supply lines to an unused wetbar sink that has no shut-off valves?
I know I need to shut-off the water at the main... after that I'm not sure how to proceed.
Do I need to install shut-off valves first?
I have replaced other faucets and installed new dual flow kits in our toilets... so,. I can follow basic instructions. But, I will need some specific instructions for this project.
Thank You.

If copper pipes cut off square and solder on a pipe cap. If CPVC pipe cut off square and glue on pipe cap.

If you do not do soldering, install a compression stop valve and close valve.

Close the main, open faucets below the level of the pipes you are working on to drain water away from your work, cut the 2 pipes, and clean and solder copper end caps on.

If the lines are still going to be accessible, a couple of 1/2 sharkbite caps would work nicely. They are push-fit fittings, that merely push on. There is also a tool to remove them if need be in the future.

Thank You to All 3 of You.. (Yes, they are copper lines), thanks for the options, will keep you posted.

All great solutions but Lee came up with the easiest one which was,
a couple of 1/2 sharkbite caps Good luck, Tom

Well, I would have said that, but I didn't know they made Sharkbite caps. I should have, Lee is just smarter than I am.

Lee is just smarter than I am. I disagree Harold! You're one of the best that we have. Regards, Tom

Check is in the mail Tom.
LOL Tom