On Super Bowl Sunday, 50 lucky fans will be on the field with R&B superstar Beyoncé during the halftime show, thanks to a Pepsi sweepstakes. Slightly less lucky winners will have their photos seen by millions during the halftime show, even though they won’t be at the Super Bowl themselves.

To win this opportunity of a lifetime, these Beyoncé fans entered photos of themselves in certain poses (like foot-tapping or confetti-throwing) — and then they provided Pepsi with personal information like their email addresses and phone numbers to use for marketing purposes.

It’s a small exchange, isn’t it? You give Pepsi some personal details in exchange for spammy emails and a miniscule chance to win a trip to one of the year’s most sensational musical performances.

Most of us don’t even think twice about this. “I’m an adult,” you think. “I’m not foolish enough to buy a product just because they are sponsoring a halftime show or because they send me an email.” It’s not as if this contest is making you drink more or less soda, is it?

But PepsiCo Inc. isn’t sponsoring a sweepstakes just to be nice. The world’s second-largest soft-drink maker wouldn’t do this if it weren’t getting something out of it, and that something is the increased sales that come with this kind of publicity boost. Pepsi knows what it’s doing.

When you enter the party-with-Beyoncé-at-the-Super-Bowl sweepstakes, you give PepsiCo permission to send you marketing materials and are invited to tweet or post on Facebook about Pepsi with a single click, thus marketing to your friends. With all of this exposure to Pepsi branding, somewhere in your psyche, advertising experts are betting you now feel friendlier toward Pepsi.

When you finish entering the sweepstakes, you reach a screen promising you 100 Pepsi points for entering. Oh, you haven’t signed up yet to accrue and redeem Pepsi points? Here, please do so now — and give Pepsi more of your information. The more Pepsi you buy, the more points you get.

Want to know one great way to improve your diet? Don’t drink Pepsi. One can has your entire daily allotment of sugar — about three tablespoons of it.

Our president and first lady ought to reconsider their relationship with Beyoncé. Celebrities who promote soft drinks undermine public health.