rats are weird sometimes

Earlier I had mopped up some spilled coffee with with a tissue, which I then -- being a slob -- just left lying around next to the mug. Just now my rat Krümel grabbed it and rather than using it for nest purposes as my rats usually do with all kinds of paper products they get their paws on, he proceded to eat the bits of tissue with coffee soaked into it. It wasn't even sugary coffee. Then again he always noses empty coffee mugs as well.