If you can stop and have access to water, then use it to refill the reservoir and turn on the engine for a few minutes until it warms up. If not, grab as much water as you can find and drain it into the radiator while doing whatever is feasible (hose, bucket) at a distance.
It’ll be simpler in cases where there is still enough coolant in levels of the coolant reservoir; add tap water to this reservoir so that there’s only an inch or two leftovers at most. Turn the car back on with those instructions just given — by being very careful not to run out of cold water before turning it off again.
Originally published on quora @sequoia-global
