At 6 p.m. there will be a reception and cash bar.

下午6点钟有招待会和饮料吧台。

It's an open bar, not cash bar.

那存不存在开放式酒吧的说法呢？

Open bar: the alternative to a cash bar.

开放吧：现金酒吧之外的另一个选择。

As I was speaking, somebody started passing a hat along the bar, and before I knew it, I was handed a fistful of cash, nearly $500.

我一边讲着，一边有人在沿着吧台传递一顶帽子，而在我没有发现的时候，有人给了我一大把现金，总共约500美元。

From that booth the men could watch the crowd at the pool tables and keep a watchful eye on Alexi near the cash register, and Nicolo drawing beers behind the bar.

从那个隔间可以看到台球桌旁那群人，同时还能盯着收银台附近的亚历克西和正在吧台后倒啤酒的尼科洛。