Since we are not given with any quantitative information, we have to rely on literature data. Suppose the soda drink referred to here is Coke. The density of a Coke at 20°C is 0.995 g/mL. A single drop of liquid is approximately 0.05 mL. From these two data, we can determine the mass of coke in a single drop.
Mass = 0.995 g/mL * 0.05 mL = 0.04975 g
We have to know the molar mass of Coke. Since majority of it is composed of sugar sucrose, let's take the value of the molar mass of sucrose: 342.2965 g/mol. Using the Avogadro's number (6.022×10²³ atoms/mol),
Number of atoms = 0.04975 g * (1 mol/342.2965 mol) * (6.022×10²³ atoms/mol) = 8.75×10¹⁹ atoms