Hydrochlorothiazide 25mg works for me.
Now I am not advocating using it for a weekend or just for the beach. It isn't going to help very much any way while you stand in the hot sun and (most likely) drink beer or sodas.
It is one of the compounds in Dyazide, which I have never really liked. I don't know why. But I just don't like it. I hate Lasix even more. But hydrochlorothiazide works the best for me. Simple. Effective. At least in regards to what I use it for. I don't really use it for appearances as I stay lean anyway.
I only use it for travel. When it comes to a long flight for my international gigs, I will take one tab in the AM on the day of the flight (no matter what time of the day I am leaving), and one tab 24 hours later - for a total of 2 tabs within two days due to the fact I always retain water if flying more than 6 hours. To me, it doesn't matter if you fly first class or standing up the entire way in the toilet stall, your body (at least in my experience) reacts to the altitude change with water retention.
I refrain from drinking alcohol or soda/juices on the plane. Avoid most salt/sugar items all together. I will have water with a half pack of Crystal Lite Lemonade that I bring with me. If flying 8-10 hours, I will have an Ambian and sleep most of the way forgoing any food along the way. The 2 tabs in 2 days method really tightens me up and does what I want it too.
If flying more than 10 hours, I will eat something that I bring with me and only pick at the food they give you on the plane. Even in first class / business class the food typical processed choices that is loaded with sodium. I will bring canned chicken with the pull off top. (Because canned tuna smells HORRIBLE as it is and 10x worse on a plane with shared air.) Or I will bring some homemade protein COOKIES. I would not advise bringing homemade protein bars because I have seen some of the attempts that you guys have made at making these yourselves and it looks remarkably like Chocolate covered C4 sprinkled with oatmeal. Wouldn't surprise me to see a video of several TSA agents (fat ones) dropping the elbows on you at security for suspicious items. LOL
But that is what I use diuretics for. Not exactly what you have in mind. If you do opt to try it for your purposes, please come back on here and report what you did, how it worked, and whether you would do it again for other people to read.