They propose that if rats in cocaine choice studies choose the alternative reward so often, it is likely because the delay to cocaine reward is longer than it is for the nondrug reward (sweetened water here)

Sugar now or cocaine later? Anne-Noël Samaha. Neuropsychopharmacology Sep 1 2020, volume 46, pages271–272(2021). https://www.nature.com/articles/s41386-020-00836-z

Rolf Degen's take: https://twitter.com/DegenRolf/status/1336722778238627840

A few years ago, I was teaching a graduate course on drugs of abuse and addiction. We were on the topic of preclinical choice studies, where laboratory rats must make a mutually exclusive choice between self-administering cocaine or an alternative reward (e.g., sweetened water, appetitive foods, or another rat to interact with). These studies consistently show that most rats prefer the nondrug reward over cocaine [1] (and over heroin or methamphetamine [2,3,4,5]). After I had reviewed these studies in my class, a student asked, ‘Does this mean that sugar is more addictive than cocaine?’. This question summed up the problem. Across species, drugs like cocaine are thought to have rewarding effects that greatly surpass those of other, nondrug rewards. So, shouldn’t most rats choose cocaine? Yet, most rats choose the other, nondrug reward instead. This is true for both sexes, and even for rats with rather extensive drug using histories.