at/in, everyday/every day

[user_gary]

I have my lunch at/in the hotel everyday/every day.

Please do help me to choose the correct options.

[mykwyner]

I have lunch in the hotel every day.

Everyday (one word) is an adjective that roughly means ordinary or commonplace. "This is not an everyday occurrence."

If you eat at the hotel, you may be eating a hot dog from the cart parked in front of the hotel. Most people, however, would find the same meaning in the sentence with either preposition.