Eat more fruit.

Eat more fruit, but eat it as solid fruit not fruit juice or fruit smoothies. Will the citric acid in it damage your teeth? No! That's the point of eating it as solid fruit, sure you release some citric acid, but only a small amount, and it's cleared from your mouth quickly. Compare that with a fruit smoothie, where all the citric acid is released AND the smoothie hangs around in your mouth for AGES.