This one is sometimes a debatable topic, and of course there’s no right or wrong when it comes to tipping habits, but I’ll tell you what we do.
You generally interact with two people during a cabana rental. One is a recreation CM - they set up the cabana, check you in, bring the sodas/water for the fridge (stocked pre-COVID, upon request at the moment), bring the fruit tray in the AM and desserts in the afternoon, and will generally check in on your during day. The other is a food/beverage CM - they are the ones taking food/drink orders.
For the food/beverage CM, they will keep a tab open so you can pay and add the tip with your preferred payment method just like if you were at a bar/restaurant.
That leaves the recreation CM. There is no financial transaction that occurs with this person, so if you opt to tip it needs to be cash.
Personally, I tip both CMs. When I’ve said that in the past someone will always be quick to come on here and say “the recreation CM is not a tipped position.” I don’t really know if they are or not, nor do I really care. If you’re going to bring waters all day, keep the fridge stocked, bring fruit and treats, and generally be a host for the day, you’re going to get a tip from us.
Just my two cents on the topic.