* Glistening gallon of golden honey
* Giant gallon gurgling with green slime
* Great gallon of gravy for the gravy train
* Glimmering gallon of gold in the garden
* Grasping for the gallon of guzzling green juice
You can also use alliteration with related words:
* Garbage gathering in a gallon can
* Growing green gardens with gallons of water
These are just a few examples, feel free to get creative and come up with your own!