Restaurant exposure -- abrasion, impact, heat, and hourly wipe down with who-knows-what cleaners (perhaps alkaline) -- would be considered severe service. Making some assumptions here: You are unlikely to find anything on the shelf at Home Depot that would be super-durable. That, in addition to the fact that most finishes take about 3 weeks to fully cure and are likely to have put in severe service before that date would possibly result in the premature failure.

If the finish is failing, you will not be very successful just putting something else over the top of it. So, sorry, I'd recommend stripping and refinishing.

Behlen's Rock Hard is an excellent varnish. Waterlox original is a similar varnish the would also be a good choice.

Another option is just to replace the tops. Restaurant furniture is incredibly inexpensive. It is also likely to be finished with materials that you are not able to get or apply unless you are a commercial finisher.