The person is more likely to die. As an option, he will fall into a coma, before that he will receive psychosis and powerful convulsions. Depends on the body.
A teaspoon is about 5-6 grams of powder. Considering that a gram is already a lot of tracks, i.e. single doses.
If you swallow this teaspoon with tea or water, then most likely it will not have a very strong effect, because cocaine is a relatively weak drug when compared to synthetics such as amphetamine or other psychostimulants. That is why the most common way is to sniff the tracks through the nose. On the other hand, a whole teaspoon is quite a lot, I don't know how many there will be in milligrams, but I think it would be enough for 4-5 good tracks. And five tracks of cocaine, if it's pure, it's pretty good, so I think there will be an effect.
But there is another way that is used much less often, but which works great for almost all drugs that can be sniffed, is to put it under your tongue and wait about five minutes until it dissolves there. The other day, a friend of mine tried to do it with cocaine and shared with me the result - it works great, the effect is almost indistinguishable if you sniff it, although in the case of cocaine it is slightly weaker. In this case, your lips and tongue will become slightly numb, but you will be very high. So, given that a teaspoon of cocaine is not enough, then you will be under the influence of the drug, almost to the same extent if you sniff 5 tracks, that is, it will be very cool.