Sneak IN, OUT, and UP

Verb do something in a hidden or secret manner
Many parents are familiar with the trick of sneaking vegetables and other healthful stuff into their kids’ food. Turns out White House chefs were using similar tricks to whip up grub for noted junk food lover Bill Clinton.
Verb enter without notice because it would not be permitted
Cedillo seemed a bit nervous about taking one more guest than he was allotted but joked that if we couldn’t get in, then the two of us (who happen to look Hispanic) could sneak in the back pretending to be hired help.
Verb come in without warning
Temperatures are near seasonable averages Monday through Wednesday. Expect sunshine to get mixed with clouds at times, and a stray shower or two could sneak in, especially to the southwestern parts of the area.
Verb leave without others knowing
Rumoured lovebirds Deepika Padukone and Ranveer Singh were spotted trying to sneak out of a posh night spot in Mumbai's Bandra area on Sunday night.
Verb approach quietly and secretly in order to avoid being noticed
According to a new study, the world's slowest swimming shark may have evolved a slick move. They sneak up on snoozing seals.