Or you could just remove the tank, and dump it.
I haven't looked at the tanks on our trucks to see how hard they are to remove. Last time I removed a tank was my 1985 S-10 Blazer that developed a leak. Who knows, on today's vehicles the instructions for removing the windshield washer tank may start like this:
STEP 1: Refer to Chapter 3, BATTERY & CHARGING SYSTEM to disconnect battery, removal of wire harness to the battery, and removal of battery and battery tray.
Step 2: Refer to Chapter 6 on REMOVAL OF ENGINE if you have a 3.6L V6 Engine, Chapter 7 on REMOVAL OF ENGINE if you have the Diesel, and Chapter 8 on REMOVAL OF ENGINE if you have the 4 cylinder gasser.
Step 3: Refer to Chapter 12, SUSPENSION, on removal of the front shocks and to suspend the suspension system in order to access the Windshield Washer Tank.
Step 4: Disconnect wire harness to the Windshield Washer Tank that provides power to the pump and the hose from the pump to the windshield spray nozzle.
Step 5: Remove 4 bolts holding tank to inner fender using 12 MM socket and gently lift tank from engine compartment, being careful to not spill contents.
Step 6: Reverse steps 1-5 in order to reassemble truck.