There is not a lot of research supporting diet and prevention or cause of kidney infection.
However, keeping a few kidney heath tips in mind may help...
If you are not dealing with any underlying kidney issues, the best way to flush the kidneys is to drink plenty of water, eat foods with a diuretic effect (cucumber, lemon, celery, beets, cabbage, parsley, tomato, watermelon, asparagus) and limit intake of animal-based proteins. If you are dealing with calcium-oxalate kidney stones then it's best to look into reducing consumption of foods high in oxalates (chocolate, okra, sweet potatoes, sesame seeds, greens, nuts, and spinach)
A good NutriBlast combo for kidney detox might be:
1 cup leafy green of choice
1/4 cup fresh cranberries
1/4 cup pomegranate seeds (or 1 cup grapes if you cannot find)
1/2 cup chopped carrot (or 1/4 small beetroot)
1/4 cup cucumber slices
2 Tbsp chopped parsley
1 tsp chlorella or spirulina (optional)
room temperature nettle tea or water to the max line
According to Mayo Clinic:
Reduce your risk of kidney infection by taking steps to prevent urinary tract infections. Women, in particular, may reduce their risk of urinary tract infections if they:
Drink plenty of fluids, especially water. Drinking fluids can help remove bacteria from your body when you urinate.
Urinate frequently. Avoid delaying urination when you feel the urge to urinate.
Empty the bladder after intercourse. Urinating as soon as possible after intercourse helps clear bacteria from the urethra, reducing your risk of infection.
Wipe carefully. Wiping from front to back after urinating and after a bowel movement helps prevent bacteria from spreading to the urethra.
Avoid using feminine products in the genital area. Using feminine products, such as deodorant sprays or douches, in your genital area can irritate your urethra.