Here are ideas for science fair projects you can do using salt or sugar:
How is the speed of sound affected by the salinity of water?
Investigate the different types of salt used as de-icing agents. Which is most cost-effective? Safest for the environment? Best at preventing ice formation? Under what condition?
Grow table salt crystals. How is crystal formation affected by rate of cooling? Saturation of the starting solution? Other factors? Other crystals you can test include sugar crystals and epsom salt crystals.
You can make a density column by making solutions with different concentrations of sugar. How is the index of refraction affected by the concentration of sugar? Can you relate the angle by which light is bent to the concentration of the solution? Is the angle by which light is bent affected by the temperature of the solution?
Which material increases the conductivity of tap water best? salt, sugar, or baking soda? What happens if you change the concentration of the solution?
There are many types of salt available at most grocery stores, including table salt, rock salt, and sea salt. Other salts you can find include epsom salts, potassium chloride (lite salt), and baking soda. Which type of salt works best for making ice cream in a baggie?
When you crush sugar crystals you can cause them to emit light. This is an example of triboluminescence. Examine triboluminescence of sugar crystals, Wint-o-Green Lifesavers™, and other candies. Which produces the brightest spark? Does the ability to produce light seem affected by other facts, such as humidity?