Set up a stall at a popular location. Put up a big banner saying that you’re giving out free soda (Coca Cola, Pepsi, Limca etc) in exchange for people filling out a survey. People (mostly those who drink sodas often) would get attracted to the stall.

The survey would ask them about the amount of sugar and other harmful contents of these drinks. They’re then told the answers to those things and made to realise the true harm. If people want, they can still take the soda (but I suppose most people likely won’t after hearing it all). Alternatively, they may pay to buy water (or another healthy drink) to quench their thirst. This could (1) be great advertising for the healthy drink (uses big names as hooks and emphasises their value proposition) and (2) be used to fund the stall and any expenses.

This seems like a great way of increasing awareness about these drinks, and specifically targets people who are more likely being harmed by the drinks. A possible concern is that some people will just come to get the soda with the intention of reselling it elsewhere; but this is easily resolved by marking the sodas with a “NOT FOR SALE” message.