It's amazing the number of things that are yellow in color that are unappealing. Lemonade is pretty great, but I wouldn't say it's a best thing in life. It's not even that yellow and it's liquid, so there's no chance of it looking like a banana. There might be a banana-shaped drink pitcher or beer mug, though. Closely related to lemonade, but produced in a completely different manner and lacking lemonade's appeal, is urine. Sure, you can pee into your radiator or write your name (poor penmanship included) in snow or even drink it if you are lost in a desert, but it's not considered a good drink. I doubt chilling it or adding sugar would improve the taste. Then again, some people go gaga over coffee beans that a cat shit out. 

When I was still a kid and living in Knoxville, I went to summer camp in Virginia. We had a huge lake with a diving tower and about a dozen sailboats of all sizes. I loved sailing. I was a skilled enough sailor to be able to solo a 13 footer that was yellow and shaped like a banana. That was a best thing in life, but not because the boat was yellow. All of my best moments on that boat, tiller in hand, ducking to avoid the boom while tacking, trimming the main for speed, were all spent where I couldn't see the yellow hull. Also, people say red makes things go faster, not yellow. 

There are plenty of unpleasant or unfortunate things that are yellow, though.