Please explain the law of diminishing marginal utility of drinking a coca cola or softdrinks.?

Question

Please explain the law of diminishing marginal utility of drinking a coca cola or softdrinks.?

Answer 1

When you're really thirsty, the marginal utility of a Coca Cola is really high, because you want to quench your thirst.  The second one will still have some marginal utility, but not as much as the first one, because you're not as thirsty as before.  Eventually, once you have too many, you'll start to get sick of them and you will stop drinking them.  At this point, a Coca Cola has negative marginal utility, because drinking one more will make you less happy.  

You can test this theory by eating at three different restaurants: one with free refills, another that charges a smaller fee, say twenty cents per refill, and another that charges the full amount for each refill.  Assuming you're equally thirsty and you're willing to pay your marginal utility for each drink, which one do you think you'll drink the most at?