Yes, even a cup of diluted cold brew stored for about a week can still be a delicious coffee drink, provided it has been stored correctly in the fridge. The process of diluting doesn't affect the shelf life of your cold brew. Nevertheless, the flavor may not be as strong as a fresh cup of your own cold brew. Always remember to trust your senses—if the taste or smell seems off, it's safer to discard your leftover cold brew and prepare a fresh batch.