>>1
Milk is made up of water, fat and milk solids. The milk solids will break down eventually, but will leave residue for quite a while which will coat the grass leaves and hamper growth. The milk fat will go rancid, it will smell bad and attract flies, wasps and other pests. The grass will not thank you for this.
Fruit juices will usually break down cleanly and, compared to milk, quickly. But due to high sugar content it will attract a lot of ants. And I mean a lot of ants. Since sugar is water soluble, this shouldn't be too problematic if there's heavy rainfall expected. If you spread it out rather than concentrating it on one spot, it won't kill the grass.
Coffee, assuming it's not hot, is benign if there's no milk or sugar involved. Grass growth can be improved by mixing coffee grounds (new or used) into the soil.