You have background in customer relations,cash management and transactions, trust was placed in you to run credit cards and receipts back and forth from customers, your memory was exercised by having to remember drinks, often times you were a set of ears to listen, maybe a shoulder to cry on and so forth.
I think that the position of bar waitress in itself may be somewhat intriguing to a potential employer as there are many facets to the job.
My opinion is that the experience you gained while doing that job was definitely beneficial in learning about day to day life.

You’re actually more experienced than you think, and I’m sure you have an array of interesting stories. Not to mention we’ve all done jobs while we’re waiting for our ‘real’ ones to come in, no one will fault you for that, especially as a college grad.

You just need to make sure you focus on the attributes of the job, rather than the specific tasks. Customer service, multi-tasking, fast paced environment, maintaining a professional yet personable relationship with both customers and co-workers, etc.

All job experience is just that, experience.

-served food and beverages to customers
-catered to customers at poker/darts and roulette tables
-provided outstanding customers service to casino patrons

not much you can say about the job so im guessing this should adequately describe it
try not to go into any details that may sound embarrasing or funny such as “satisfied patrons’ every need”