Practicing Jains eat consciously. This is a small percentage of people now. All living beings have a soul, this is the basis of a Jain diet.
Keeping this in mind, Jains are fruitatarians - eating whatever stuff that comes off of a tree and requires minimal violence. For example, Jains avoid root vegetables of all types because when you uproot an onion that entire being’s life is gone - you’ve essentially killed it without the possibility of rebirth.
Now, there’s a deeper and even more meaningful reason behind not eating roots according to Jain texts, root vegetables contain infinite microorganism called nigodas. These are one-sensed beings (all souls) and exist within a potato, onion, carrot in an infinite amount. It is said that millions and millions of nigodas occupy the space within an onion/garlic/potato - and not just this - millions of nigodas having short life spans take birth and die in that very space in microseconds.
Now, this is ancient scriptural information which I don’t expect most laypeople to understand or fathom. For Jains, this is a truth that we’ve grown up knowing and experiencing.
And there are sects of Hinduism & Buddhism that follow the same logic and principles in avoiding the intake of root vegetables- in particular onions & garlic.
The basis of Jain life is that one should experience Bliss only from within. Any happiness coming from external sources is still in fact engaging the soul within where happiness comes from. “The department of happiness, in life, belongs only to the soul.”
Because if happiness existed outside then all people would get satisfaction out of the same things. But this is never the truth.
So, Jain eating fundamentally believes in eating for survival and not for taste. And if there is taste recognize that the joy we experience is coming from within. And furthermore, the idea is to be rid of our momentary pleasures and unlock the treasure chest of infinite Bliss from the soul.
I hope that gives you an idea of the Jain diet. =)