With all power yachts and most sail yachts, you start with a full diesel tank and have to refill it before you return the boat.
Moorings sail yachts are an exception within the Caribbean; they usually include fuel for a fee. For both Sunsail and TMM non-generator yachts, they have a pre-pay option, so you don’t need to refill the tank if you don’t want to.
Read more on Bareboat Chartering