By 'café léger', do you mean watery coffee? I can't think of any term that's specific to coffee, though I've often heard very weak or watery tea, coffee or beer referred to as(or). Not particularly sophisticated descriptions, but they get to the pointMy favourite coffee-related put-down comes from the British comedy series 'Blackadder'. The main character enters his dingy local coffee shop, greets the owner and calls for "a cup of your best hot water with brown grit in it. Unless, of course, by some miracle, your coffee shop has started selling coffee."