Yes, sweeter is a Scrabble word!

Adjective

1. Having or denoting the characteristic taste of sugar

2. Having a sweet nature befitting an angel or cherub

3. Pleasing to the ear

4. Pleasing to the senses

5. Pleasing to the mind or feeling

6. Having a natural fragrance

7. (used of wines) having a high residual sugar content

8. Not containing or composed of salt water

9. Not soured or preserved

10. With sweetening added