I'll add to this, there's no reason to buy simple syrup! You can make it in a mug in the microwave in 30s, and it'll hold in the fridge for a while.

And the only counterpoint is pineapple juice, which you should just buy in the can -- it doesn't hold long at all once in air.

Absolutely make your own syrups! If you add a little bit of alcohol to your simple syrup (I use vodka or a clean rum), you can drastically extend the shelf life.

Honey syrup is even easier to make, just mix 50/50 honey and hot water. Subbing for simple syrup gives interesting results in most drinks.

Grenadine is also super easy - buy a bottle of POM and mix juice 50:50 with sugar. I like to add a little pomegranate molasses (get at a middle-east specialty market) to kick up the flavor, but not necessary.

Re: pineapple. If you are able to press your own pineapple juice you absolutely should, but agree that most people do not have the necessary equipment. Trader Joe’s sells bottles of fresh pressed pineapple juice that is excellent, if you’re fortunate enough to live by one. Otherwise yeah, canned is the way to go.

Sometimes I just make a Tbsp or two of simple syrup in a shot glass in the microwave. It takes about 10 seconds.