What happens if you varnish laminate flooring

It depends on the type of laminate. Some of the early styles were glued t&g if this is the style you have I might try a poly coat depending on the surface material, some are not wood and may not play well with poly, oil or latex. Of the wood and bamboo glued floors I installed poly did help. Note do not sand with a drum sander the veneer is very thin. If it is a snap lock floor I would not try to use poly as this kind of floor flexes and the poly in the gaps will probably chip along the lines and look worse but I do not know this as a fact, the one house that the renter tried to fix the floor tried to sand it prior to varnishing but had taken the surface layer off , then left knowing their deposit was less than the damage they caused.

If you know it's a Formica type faced flooring, then your only real bet is Rustoleum's Clear spray paint. The stuff is fantastic and quite durable. I've used it to "paint" laminated cabinets and countertops to restore warn and dull areas. I also use it on aluminum ladders to kill aluminum's marking abilities.

However, if it's quality flooring and real wood of a 16th or more thickness. Then, it can absolutely be stripped or sanded and treated like real wood. I highly recommend Bona Traffic HD Commercial as the finish product.