B, the pH value of apple is 2.6 ~ 3.7, which is acidic. Patients with hyperacidity should not eat, so B is wrong;
C, the pH value of milk is 6.3 ~ 6.6, which is acidic. Patients with hyperacidity should not eat, so C is wrong;
D, the pH value of corn porridge is 6.8 ~ 8.0, which is close to neutral and can be weakly alkaline. Patients with hyperacidity can eat, so D is correct;
So choose D.