The amount of sugar in a liquid can be measured using a laser pointer and a prism. Basically, you utilize Snell's Law:
n_i*sin(θi) = n_r*sin(θr), where,
n_i = index of refraction of the incident medium
n_r = index of refraction of the refractive medium
θi = angle of incidence
θr = angle of refraction
You make use of the laser pointer, prism, and sugar solutions in various known concentrations. You then graph the sugar concentration versus the angle of refraction. You can then determine the amount of sugar in a liquid after determining the angle of refraction of that unknown sugar solution.