Use a rain barrel for watering and vehicle cleaning
It’s reasonably easy to capture rainwater, and save it for watering plants or washing vehicles. This reduces how much water has to be treated and pumped by your municipality, and provides untreated water for your plants.
Set a rain barrel on a sturdy surface (since water is heavy) and direct your downspout(s) into the barrel. You can use a tap and/or hose to get the water to your garden. Be sure that your rain barrels are set up to overflow away from buildings. Check out CMHC’s advice on rainwater harvesting. Note that they include using the water for some indoor uses which may not be permitted in your area.