If you are fortunate enough to have an outdoor space, consider having a BBQ every Friday afternoon between 3pm - 5pm. Feature something different every time. Have your chef out on the BBQ chatting with guests as he/she cooks up the BBQ feast!
Casual and personal is what this event should relate to your customers. Beer, cooler and cold drink sales will benefit, relationships will develope with customers on a more casual level, and you will generate revenue on a, more than likely, slow time of day.