The most common and most likely answer to this crossword clue is the 8 letter word ICEPACKS
I've seen this crossword clue in Financial Times
I
C
E
P
A
C
K
S
Buddy explains!

The straight part
We know that "cool bags" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cool bags = icepacks.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ICEPACKS mean?
ICEPACKS noun- A large floating mass of ice; pack ice.
- A pack of crushed ice applied to the body in order to reduce pain or inflammation.
- A plastic sac of silicone that can be cooled in a freezer and then used in a cool bag, cool box or cooler; a freezer block