You either have a bad cooler or you open it too much. Use more than one
cooler. One that is opened only 1 or two times a day and a 2nd that you use
for the drinks and diving in to. Load it each day from the cold cooler.
Probably open it a lot. At any given time there are at least a dozen on
our race team racing in. On weekends when I am in charge of drinks, I
bring three to four cases of water and gatoraide.