Dear Rabbi Simon,
There aren’t many items which have a kashrut symbol where I live. I want to get some energy drinks. What should I look out for to avoid non-kosher drinks?
TY for your question.
My best practical advice is to make use of the Is It Kosher? app https://isitkosher.uk/. This has extensive lists of food and beverage items in all categories, including energy drinks.
In general, beverages may be problematic due to grape derivatives and objectionable E-numbers, such as the infamous E-120, referring to a naturally occurring red colour derived from the cochineal beetle. Visit https://www.kosher.org.uk/article/which-enumbers-additives-are-not-allowed for more info. Note that some beverages can contain milk as well.
However, shared equipment means that one cannot always rely on the ingredient panel alone. For this reason, it is proper to choose an energy drink which actually appears on the approved list. There are lots of them.
Rabbi Rashi Simon