Effect of meal temperature on gastric emptying of liquids in man (Gut, 1988):
The initial rate of gastric emptying of the cold drink was
significantly slower than the control drink…
The slower the gastric emptying of a drink, the slower delivery of glucose to the small intestine, where it is absorbed.
So, glucose from a cold drink will be absorbed slower than glucose from a room temperature drink, which may delay the treatment of hypoglycemia, but probably not more than for several minutes.
Glucose from a hot drink will be also absorbed slower, because the stomach needs to cool it down to body temperature before letting it through. So, theoretically, the ideal temperature of a glucose solution to drink to treat hypoglycemia is 37 °C (body temperature).
Some say the beverage temperature does not signifficantly affect gastric emptying, though:
Fate of ingested fluids: factors affecting gastric emptying and intestinal absorption of beverages in human (Nutrition Reviews, 2015):
Beverage temperature that differs markedly from normothermia has
little effect on gastric emptying as intragastric temperatures rapidly
After checking several articles about treatment of hypoglycemia in diabetics, no one mentions the temperature of a drink, which suggets that this may not be that crucial.