I would r respond like :

"Hey ! Even I also had the same doubt. So I had researched about and found a brand called POCA , they make flavoured syrup which are plant based with zero sugar , added fibers. I was not expecting it to be true , but when it arrived and I gave it a try ! And surely they do what they say ! It's really 0 sugar and the flavours they offer are real good too. Ive been using POCA ever since and I would highly suggest you to give it a try too ! It wouldn't disappoint"

I have previously done promotions in many subreddits about my own app. And I do have certain experience about what gets a promotion without down voting.

I first start with a real life problem , which everyone on that community has in common and then slowly as the reader graduates into reading the post, a subtle promotion about the brand should be done , not like " This brand helps you with xyz" but like "— I've been facing the same problems, but untill recently when I came across this brand, I decided to give it a try. And it is really working for me".

Promotion should be done subtly. I've seen posts which were clearly shouting "THIS IS A PROMOTION" just by reading the posts tittle.

Username: u/AromaticClassic79

Karma points : 500

I have recently started using reddit, since this account is 3 years old— i forgot the password for it. And since last 1-2 weeks I've started using reddit regularly again.