सेब को खाइए l
Its more like an advice I guess. Like a doctor say - "Eat an apple".
Stress on apple.
सेब खाइए l
Its more like if someone asked what should I eat. You would say - "Eat an apple".
without any stress.
But in general most people use them interchangeably without even noticing.
Another example -
I work at a bank.
I work for a bank.
I work in a bank.
In Hindi all of these translates to -
में बैंक में काम करता हूँ | (Mein bank mein kaam karta hoon.)