In the case of prom, only you will be able to ensure that your drink is by no means spiked at all. However, there is a simple way that you can keep your drink “pure” for the most part. The thing is that perpetrators that spike drinks are very opportunistic. They will try to spike your drink at any given moment for the most part. Still, there are ways and means to keep that from happening for the most part.
The first thing you need to do is make sure that your prom date is a person that you can trust. You can trust him/her to not spike your drink. If you want to go to the bathroom or do something else, your prom date can make sure that nobody messes with your. Even if you look away from your drink for just one second, it is more than enough for the perpetrator to slip something into your drink. If there are plenty of distractions, that gives the perpetrator more time to really spike your drink.
If you went to prom by yourself, you will have to keep an eye on your drink at all times. If you have to go from “Point A” to “Point B,” be sure to carry your drink on you at all times. This is in case the only drink available would be punch. If they have canned drinks, drink from one can, toss that out, and grab another can.
The best method would be to implement a buddy system with you and your friends. It is not uncommon for couples to go out to dinner together before going to the prom. Prior to pre-prom dinner plans, plan a buddy system. During prom, people dance and socialize with each other. If you need to go to the bathroom, go out onto the dance floor, go outside and use the phone, and so forth, ensure that your friends look after your drink.
If you are a high school junior, you could probably join the prom committee. During the prom, you can have people take shifts to keep an eye on the drinks and refreshments. That way, you will constantly have eyes on the punch bowl. Not many people will attempt to spike the punch bowl.
Other than that, the best way is to keep constant eyes on your drink. If you leave your drink on the table, do not avert your eyes from it. Only you can keep your drink from being spiked.