Three ingredients, no sugar-bomb mix — tequila, fresh lime, and agave nectar.
Agave nectar is a natural choice here for two reasons. First, it comes from the same agave plant as tequila, so there's a flavour affinity — it amplifies rather than competes. Second, it's about 1.5 times sweeter than sugar by weight, so you need less of it, which reduces both calories and sweetness.
Use light agave nectar rather than amber — amber agave has a more caramel, molasses flavour that can overpower the lime. If you don't have agave, honey syrup (1:1 honey and warm water) is the next best option.
Add 2 slices of jalapeño to the shaker and muddle before adding everything else. Heat adds flavour complexity without calories.
Muddle 4 fresh strawberries in the shaker before adding the other ingredients. The strawberry adds natural sweetness — you may want to reduce or eliminate the agave nectar.
Add 3 slices of cucumber to the shaker. Muddle lightly, then add everything else. Refreshing and very clean-tasting.
Replace ½ oz of lime juice with fresh watermelon juice. Sweet without adding sugar, and the colour is stunning.