I live in a home where I am the only one keeping kosher. Foods like rice, grapes, and apples are washed or soaked before eating. Inevitably, water will splash from the sink back onto the food. Does that water from the non-kosher sink render the food non-kosher (cooked and uncooked)?

ב"ה Shalom and Happy Pessach= Passover Kosher food, primarily can be come non-kosher when non-kosher ingredients are added to the kosher food, or if the kosher food was cooked in a non-kosher utensil. (There are other ways which I won't get into in this answer). Therefore, if only some water splashed onto your apples, grapes or rice, they do not become non-kosher, since the water is not boiling. Furthermore, water splashed from the sink may be mixed with soap or other foul substances, thereby rendering the water unpalatable, and consequently such water would not render the food non-kosher. Nevertheless, to avoid all possible scenarios of your kosher food being mixed or touched by non- kosher food, it is best to keep your kosher food at a safe distance from the sink or anywhere else where splashing or mixing may occur. All the best