Teaching kids about the sugar content of common drinks should be a requirement in kindergarten or first grade. Here’s one way: have the class construct a display for the hallway or classroom wall that visually shows how much sugar is hidden in common beverages. Like this:

Ideally, also include sweetened milk, apple juice, orange juice, and Gatorade.
Poster titles matter, too. “Rethink your drink” is a popular title (it rhymes) but is bland and doesn’t suggest that drinking less sugar is the ideal. “Avoid cavities by avoiding sugary drinks” or “Don’t drink dessert all day” might be more engaging and informative.
This project would fit in perfectly with most state standards (for example, see page 10 in Health Education Content Standards for California Public Schools). And because it includes numbers (of teaspoons), teachers can use the poster content to visually drive discussions about addition and subtraction. If this poster was done in a fun way, the experience might vaccinate kids against over-consumption of sugary drinks for the remainder of their lives.
If you want some background information relevant to lesson plans on sugar for K-3 levels, here are some resources from BrainPOP. You can pitch the poster completely in terms of dental health. If you are brave and tenured, make the point that drinking sugary beverages causes kids to consume more calories than they expend.
Here are some examples I’ve collected onto a Pinterest board:
Pinterest board Educating kindergartners about sugary drinks on Pinterest.
Here is another example for your collection (spotted at a library):
http://ushealthykids.org/2014/04/01/a-public-health-tale-of-two-libraries/
The messaging with children has to be carefully worded or the teacher may face backlash for fat-shaming or instilling a diet mentality in kids. It’s a tricky balancing act even as a parent working to teach my own children.
I’m totally for “eating right and moving move,” but that message has clearly failed to change children’s behavior. Sure, all the kids — even the obese ones — can probably recite such phrases, but in the end most still go home to drink soda, snack ad libitum, eat adult portions, and sit on the couch watching television until bed time. Teachers need to convince young kids that going through life fat is unhealthy. Really unhealthy. It’s a simple message (potentially), just like lesson plans that could be about smoking or looking both ways before you cross the street. Currently, kids are simply not getting the message about excess weight. They are getting “I’m going to grow out of it in high school!” or “if I move a lot, I can be a healthy fat!”. It’s of course fear of the backlash, as you mention, that prevents a more honest and more effective education on the topic. And that’s why superintendents, principals, and district Wellness Committees need to charge teachers with getting to the point, and getting creative about getting kids’ full attention. There’s always going to be overweight and obese kids in the room, of course, but avoiding the truth (until high school, when it’s far too late) does a disservice to all kids, even the currently, temporarily thin. We need to get beyond the “fat-shaming” block somehow. Weight IS the issue, not just the proxies of diet and activity, both of which affect weight. Education about healthy weight can be done with sensitivity, of course, but discussion of weight really needs to become part of the conversation, not just bland “let’s move!” campaigns that avoid the issue entirely. That’s my 2 cents.