Iced (cold) coffee stronger than hot? Generally, it is a fact that hot drinks make us calm. That is the suggestion from doctors - to drink a hot drink before going to bed. So, is iced coffee stronger because that triggers our metabolism?

From the sources so far (searching on cold VS hot coffee) I have found this:


  Grab a cold-brewed coffee before going to the gym. Yes – coffee made
  from cold water. Surprisingly, cold brew coffee contains many
  antioxidants and healthy body boosters for better workouts. Skip the
  shakes and vitamin waters – simply power-up with a cold brew and head
  for the gym.


The link is given here:
http://www.madescolabs.com/accelerate-your-weight-loss-goals-with-cold-brew-coffee/

I am guessing the cold coffee is stronger because of the temperature (metabolism trigger) and not because of a chemical reaction with the substances.

PS: Some examples of cold (iced) coffee can be:

a) The greek frappe which is instant coffee (nescafe mainly), shaken with water and with extra ice cubes added.

b) Freddo Espresso (cold Espresso) which is a double Espresso coffee. It is then blended for 8-10 seconds with 3 big ice cubes. That releases some flavours and the final result is poured into a glass with 1-2 ice cubes.
Stronger: No. Subltle differences: Yes.

For people who tolerate caffeine, want the longevity benefits, and looking for something gentler on your stomach with slightly less caffeine, cold brew is your cup of joe.

Hot brewed coffee has more anti-oxidants and a lower pH.  Cold-brewed has less acid and thus for many palates is 'milder'.  The caffeine content of the 2 is basically the same.

In summary:

'Hot brewed coffee could be better for you than cold, since heating it could increase the availability of antioxidants in your cup — but more research is needed to determine if the benefits are significant enough to warrant making the switch.' The individual's palate so for should be the final arbiter.

https://coach.nine.com.au/2017/09/20/09/51/cold-brew-coffee-health-benefits
https://www.mindbodygreen.com/articles/is-cold-brew-coffee-better-for-you-than-regular-coffee