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.
he is a stalker
Queen Hatshepsut sneakily usurped the title of "Egyptian Pharaoh" from her son Thutmose III, the original heir to the throne.
The suffixes for the root word "sneaky" can be "-er" (sneakier), "-est" (sneakiest), "-ly" (sneakily), and "-ness" (sneakiness).