★★★★★
Simply get a fresh pineapple, cut it into bite-sized chunks and place them on a plate out of direct sunlight. You may want to cover them just in case.
Every day, eat a piece of pineapple (or two... Or three). It's easy as that!
After a few days if it starts tasting strange/bad or looks that way - don't eat it. Otherwise, bon appetit!
The idea behind this is that raw pineapple contains a bunch of digestive enzymes called bromelain. If you leave it out in the air, it will slowly and gently culture with wild yeasts in the air - these also contain digestive enzymes. It's not going to cure any big digestive problems, but it is gentle, simple, effective, cheap and natural.
Pineapple is also a great anti-inflammatory, anti-histamine and diuretic.