If you want optimal digestion kefir water is the way to go. It is full of probiotics. These friendly bacteria will populate your gut, out-completing pathogenic bacteria and yeasts, like Candida.
To start you will need to get water kefir crystals from a friend or order online. Once you have them:
Put 1 cup crystals in a litre (quart) glass jar along with 1/2 cup raw sugar, a pinch of bi-carb/baking soda, and half a lemon. Place lid on jar (non-metal) and leave in a cool place for 3 days.
After 3 days, strain liquid through a sieve into another glass jar. Flavor with seasonal fruits, herbs and/or spices, like:
Apple and cinnamon quill
Raspberry and vanilla
Ginger, tumeric and lemon
Place lid on jar and leave in a cool place for an additional 2 days. This will ensure all the sugar is converted to carbon dioxide (that's why it's bubbly) by the bacteria.
After 2 days, pop in the fridge and enjoy!