Before automatic ice makers, people use to fill ice trays with water and store them in the freezer for a hot summer day!
Rather than letting old ice cube trays sit around collecting dust, try one of these brilliant DIY hacks:
Make iced coffee
Pour hot, fresh-brewed coffee into ice cube trays and then store them in the freezer for 2-4 hours. The coffee will freeze and then you will be to drink iced coffee whenever you need!