Water, comprising about 96% of the final product, is a key ingredient. While some brewers like to evoke images of pristine glacier fed springs, effectively, water is an easy ingredient to modify by filtration (usually to remove chlorine) or the addition/subtraction of salts. Hard water tends to be more appropriate to ales while soft water compliments the subtler flavour profile of a lager.
The early Egyptians drank their beer through reeds or tubes so they would not choke on the barley husks left in the unfiltered brew. Many of the ruling class had golden straws made for sipping their beer.