I need 1/4 cup of milk but don't have any. What can I use in place of milk?

For what? Things like Mac and cheese I'd use extra butter and a splash of water

Mayo mixed with water

Water

Ketchup

Depends on what you need it for.

half and half

My go-to is yogurt..

Read:

https://www.thespruceeats.com/milk-substitutes-for-baking-and-cooking-4155699

Depends on what you’re making. I’ve used plain yogurt in place of milk when making biscuits, and it made some fine biscuits.

you should probably just google "what to replace milk with"

Coffee whitener added to a cup of water. Cheers!

Protein powder and water.

What are you making?