This is not a sign for a puppy rescue group but merely an offering from a hot dog establishment. The problem is that as one word, “everyday” is an adjective: “Eating a hot dog is an everyday habit.” What kind of habit (noun)? An everyday (adjective) one.
However, this sign needed to make it two words. Every day you can get a hot dog for $3.50. Which day? Every day. In this sense, “every” is an adjective modifying the noun “day.”
Go and sin no more.
