If someone says "you smell like milk," it means someone thinks you've "just been suckling from mother's tit", which is meant to imply that you're naïve, young, unqualified, or innocent.
"Why you comin' home at five in the morn'? Somethin's goin' awn, lemme smell yo dick. Don't playme like a foo', 'cuz dat ain't coo'. What you need to do is lemme smell yo dick."
A check done by men during foreplay to see if a chick is clean enough to eat out. The guy fingers the chick's pussy and then he gets his fingers back into range of his nose to sniff without the chick noticing. It is easily done behind her back while kissing the side of her neck