eat the food, but sneakily
No. Sneakily would be an adverb. Remember, adjectives enhance nouns. "The big dog," "the puffy cloud." Adverbs enhance verbs. "He sneakily stole a cookie."
sneakily
sneakily, clandestinely
Yes, it means done in a sneaky manner.
quietly, sneakily, furtively, secretly, covertly, surreptitiously ..
slyly/sneakily/manipulatively
that he is so into you
No, it is not ethical to sneakily introduce a wild card during a game.
Example: "I found him lurking in the woods" Lurking means hiding, hanging around sneakily or surreptitiously, etc.
Queen Hatshepsut sneakily usurped the title of "Egyptian Pharaoh" from her son Thutmose III, the original heir to the throne.
he is a stalker
The palindrome "peek" means to look quickly and sneakily.