I find adding a packet of "True Lemon" to my water helps it go down much faster! It's pure dried lemon, not a sugary additive, so it's zero calories, just like a real splash of lemon!
True Lemon can be found in grocery stores in the baking aisle. Super tasty, although of course it's a tad sour. One pack for 8 - 10 oz. works great.