Use a milk jug as an ice pack for coolers. Fill it with water as is or after flattening it, then freeze it to turn the liquid to ice and store the cold pack in cooler bags.
Turn a milk jug into a watering can by poking holes in its cap and another one in its upper handle so the air flows through allowing the water to pour out.
You can grow your seedlings in old milk jugs for a windowsill garden. Use the jug's bottom half and add holes in the bottom for drainage, then add soil and seeds.
Transform a milk jug into a planter drip tray. Mark 3 inches from the bottom and cut, paint it to match the pot, and place a plant pot into the tray to catch excess water.
To turn your milk jug into a makeshift scoop, cut around the handle, outline the shovel shape, and snip. The sturdy plastic makes a great scoop for items like pet food.