Iced drinks are an evolutionarily recent cultural habit. It became fashionable to put ice in drinks in the 1930’s and 1940’s to demonstrate that you were wealthy and trendy enough to own a freezer.
While you may be in the habit of putting ice in your drinks, the stomach does not enjoy iced drinks at all. It challenges our ability to regulate our temperature, contracts the stomach and slows digestion, and has been shown to increase nasal congestion.
All in all, this is a helpful thing to avoid in Stage 1 and probably in general.