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“a drink” contains roughly the same amount of alcohol regardless of type, so a daiquiri should get you about as inebriated as a beer.
Some caveats: since drunk people drink more, some places have specials earlier in the evening or on some drinks where you can make it a double for no or low upcharge. That glass now has two drinks in it.
Some drinks are easier to drink fast, which makes you feel the effects faster and stronger, so you might perceive yourself to be “more drunk”, even though it’s really just hitting you all at once. Delicious sugary drinks that mask the alcohol flavor are notorious for that.
It takes about an hour to process a drink; sugary drinks will inevitably give you an upset stomach; water and food help keep your stomach settled ; you’ll have a better time not having a drink you could have and feeling good than having a drink your shouldn’t have and feeling gross, so if in doubt say nah.
You’ll be fine with one with a meal with someone you know. A second is probably fine in the circumstances but more than that is iffy.
I mean, you have your answer right there. It’s not like Harvard is a particularly untrustworthy source for diet recommendations.
Why are you doubting the number? If you feel fine and don’t want to change, don’t. Everybody is different and has different needs, and you might just need less, but anyone reputable is going to give the same rough range.