I try not to waste food or drinks in my house, so when my son left an almost full glass of milk on the table after breakfast, I decided to pour that into my coffee cup. Milk however, should not go "plop!"
(My kids are currently enjoying "Vita Worm" vitamins. My daughter tried to toss one onto her brother's plate in the morning but missed--it landed in his cup. She gave him another one and he never knew--nor did I, until I almost had vitamin-enriched coffee!)