slip in vs sneak in

slip in and sneak in both are verbs.

Word	Noun	Adjective	Verb	Adverb
slip in	No	No	Yes	No
sneak in	No	No	Yes	No

As verbs, slip in and sneak in are synonyms defined as:

Other synonyms of slip in include insert, stick in.

slip in (verb)	sneak in (verb)
insert casually	insert casually
	enter surreptitiously