There are 33.82 ounces of water in 1 liter. One fluid ounce is 29.57 milliliters. In this particular case, the number of fluid ounces equals the number of avoirdupois ounces.
Fluid ounces are a measure of volume while avoirdupois ounces measure weight. The definition of a fluid ounce is 1 ounce, by weight, of distilled water at 62 degrees Fahrenheit. If the liquid one measures is something other than water, calculating weight from volume requires use of density. In practical application, liquids are measured using fluid ounces while dry materials are measured using avoirdupois ounces. Thus, the soda in a can marked 12 fluid ounces does not weigh 12 ounces.