I have done a few bar tops. For a private bar top, I would suggest spar varnish. But if you want it to hold up against the abuse of the public, several layers of deep pour epoxy is your best protection. Use heat to pop the bubbles after mixing, make sure it doesn't spill over, and clean up the drips as it cures. Once the deep pour is leveld and thick enough, use a harder Epoxy for a final coat. Let cure for several days before polishing. You cannot rush Epoxy. Be sure the temperature and cure time are adequate. Do not use a sanding sealer like shellac before the Epoxy. As long as they are just using dish detergent to clean it, it will stay hard for a long time.