What would make a garage floor sweat. Had a very humid day here today and the garage floor looks like the hose was turned on. Checked a few neighbors garage floor and nothing.

Simple... High enough humidity to condense on the relatively cool cement.

Exactly - a concrete slab on grade will have a temperture near the 55F of the earth below it if not exposed for adequate time to an ambient temperature significantly higher or lower. My guess is that your garage was closed while the neighbors' garages were open/ventilated and/or temperture controlled.

While I understand this my point is the neighbor garage, 50 yards away dry as a bone. Mine extremely wet. Never seen anything like this

Many times air flow plays a role as well. As Clint suggested, their's may have been open to the air, and/or for some reason their slab was warmer. Pretty hard to tell now.

In fact, my house in Chicago's entry vestibule had condensation just in one corner a few days ago. Four walls brick, stone floor. Dead air space where it was damp. And the garage there OFTEN will have wet areas when the ambient conditions are right.

But barring a leak (which would be obvious), condensation is your source. Especially with the warm moist air you guys had then.