The Tastee-Cleen food sanitizer has a passive effect on the user's food items as long as it is in their inventory. While in the inventory, the food sanitizer will increase the HP value restored by most consumables by 20%.
Equation: Initial HP x 1.2 (or 120%) = final amount of HP
Example: Nuka-Cola 10 HP x 1.2 = 12 HP
The food sanitizer has no effect on other types of consumables, and will not reduce any adverse effects, such as the food's radiation rating. Furthermore, it has no effect on purified water, the alien food found on Mothership Zeta, and the slop dished out in the Pitt. It does work on Punga fruit from the Point Lookout add-on.
It is awarded after finding the medicine in the Super-Duper Mart as part of the Wasteland Survival Guide quest, along with the sanitizer instructions. According to the sanitizer instructions, it will cleanse most food and drink in the user's inventory of harmful bacteria, allowing greater nutritional gain. The food sanitizer is not a quest item, and as such will be temporarily removed from the inventory in certain situations.