Water from my furnace
Although the exhaust gases are venting vertically outside the furnace, inside the furnace the gases are drawn by the inducer motor through an "S" configuration in the heat exchanger which keeps the hot vent gases in the exchanger much longer than it would if the gases were to vent straight up and out the furnace vent pipe.
In other words, the vent gases are actually traveling mostly horizontally through the heat exchanger. The inducer motor maintains a constant draft so the flames do not smother. By the time the vent gases exit the furnace, the temperature of the vent gases have dropped so much that they actual condensate water.