Fiber Drink that are homogenous solutions I have come to know fiber as either insoluble fiber, which doesn't disolve completely in water, and therefore doesn't make a homogenous solution, or soluble fiber, which does dissolve but also gels up.

I have known for a while a drink that considers itself to be a fiber drink; however, it's completely homogenous and liquid (not a gel). So my question is, can this actually be a fiber drink? from the definitions I mentioned above! I am curious because there is a recipe that asks for this specific type of drink, and I am wondering if I could use a different kind of fiber drink. I am wondering how this type of fiber drink is different than others.

If you are wondering what the drink is, the name is called Miero Fiber (미에로화이바). It is a Korean drink.
Think soluble fiber. The following excerpt from WebMD explains very well the difference between soluble and insoluble fiber and lists foods where each can be found.

Soluble vs. Insoluble Fiber
Soluble fiber dissolves in water. Insoluble fiber does not. [...]
Soluble fibers attract water and form a gel. [...]