Well, then you can't call it a water fast. 15 days is a great achievement. If you are breaking your fast, start with a citrus fruit juice, organic orange squeezed in some water will be ideal. Then ease into eating some whole organic fruits and later in the week salad without dressing. Eat plant based diet for 1.5X the length of your fast.
If you want to continue fasting then nothing but water goes in your body. No teeth brushing or mouth washes.