Just swallow this pill like eating something.

Better say: Simply swallow this pill as if it were food.

I ached this morning, but now I feel better.

Better say: I was achy this morning, but I'm feeling better today.

She ran into the shop to avoid rain.

Better say: She ran into the shop to avoid the rain. (*Put article "the" to make the sentence grammatically correct.) 

Fine dust became one of the most important environment problems.

Better say: Fine dust has become one of the most serious environmental issues.

You have to get a shot three times a week apart.

Better say: You must get a shot three times a week.

This medicine can't ease this pacient's pain.

Better say: This medicine will not ease the patient's pain. 

After he listened that saying, his complexion is getting dark.

Better say: His complexion has darkened since he heard that statement.

Without lipstick, her face will be pale.

Better say: Her face will be paler without lipstick.

Despite diabetes, he can't stop eating jelly.

Better say: He can't stop eating jelly despite having diabetes.

The cookies that she made taste awful.

Better say: The cookies she made taste awful. 

You must not give sweets as they want.

Better say: You must not give them as many sweets as they desire.

While people know instant food is not good health, they eat it.

Better say: People eat instant food while knowing it is bad for their health.