Yes, adding a small amount of vinegar to rice while boiling can improve its texture, making it fluffier and less sticky. It can also help keep the rice grains separate.
Adding vinegar to rice during the cooking process has several benefits. The acetic acid in vinegar helps to break down the starches on the surface of the rice grains. This prevents the grains from sticking together as much, resulting in a fluffier texture. The vinegar also slightly lowers the pH of the cooking water, which can further inhibit starch gelatinization and clumping. A general guideline is to add about 1 teaspoon of white vinegar per cup of uncooked rice. Stir the vinegar into the water before adding the rice and bringing it to a boil. Cook the rice as you normally would, following the package instructions or your preferred method. You won't taste the vinegar in the finished rice, as the small amount used dissipates during cooking.
Don't add too much vinegar! Using more than the recommended amount (about 1 teaspoon per cup of rice) can make the rice taste slightly acidic. Start with a small amount and adjust to your preference in future batches.