Here's a simple dessert that requires no added sugar.
Whip a 1/2 can of coconut milk as you would regular whipped cream. It tends to come out thinner, as you might guess. Click here for an example of how to make it come out thicker (hint: refrigerate the can of coconut overnight). Sweeten with liquid stevia, if desired.
Cut a full slice of ripe watermelon into four to six wedges. Top with whipped coconut milk. Add sliced strawberries, sliced grapes, and unsweetened coconut flakes. Chill till ready to serve.