so happy to hear you enjoyed the game! And by the comment it sounds like you got a hang of it too! We were a bit worried that people would not understand how it works. In very last minute before the game was published we added the help text on day 1.
The freedom of the drinks was to allow players to add more ingredients extra "free of charge" to their customers to increase the relationship with your regular customers by adding things they like.
The better relationship the more they tip. Also, don't forget to talk to them to get to know them better. Maxing out the relationship will guarantee a tip and you are sure to have enough revenue to withstand the rent.