Not everyone advises this. Caffeine helps with so-called orthostatic hypotension. That is, with low blood pressure in the vertical position of the body.
Normally, when moving from horizontal to vertical position, a reflex is triggered and does not allow too much blood to rush down to the legs.
With orthostatic the hypotension reflex does not work well. Blood rushes downward and blood pressure drops.
Caffeine tends to stimulate these reflexes. Therefore, it helps with orthostatic hypotension.
On the other hand, caffeine is harmful in reflex fainting. If people faint in a stuffy room, then this is due, on the contrary, to the launch of a harmful reflex. Blood pressure during fainting is also low, but caffeine only makes it worse. Because caffeine provokes any reflexes - both good and bad.
These drinks contain caffeine, therefore they have the effect of vasodilation, therefore they are advised for those who have hypotension, but need to be without fanaticism in everything.