"... make lemonade."
Somebody doesn't know the recipe for lemonade. It's equal parts lemon juice and sugar, water to taste. The saying also requires that life gives you sugar in equal proportion to how many lemons you've been given. In which case, it's simply being pessimistic. "When life gives you sugar, make lemonade." Somehow that doesn't sound as deep and symbolic. It sounds like one of many uses for sugar. The reverse claim that life has given you lemons and you mysteriously pull equal amounts of sugar from thin air, is supposed to be somehow deep?
When life gives you lemons, make lemon meringue pie!
When life gives you lemons, make lemon peel candy!
When life gives you lemons, use them as a garnish for alcoholic beverages.
And since we're pulling magical allegorically good ingredients out of thin air, why not just ignore the premise.
When life gives you lemons, eat sugar.
When life gives you lemons, make yourself a sandwich.
When life gives you lemons, listen to people tell you stupid things that they haven't spent very long paying any attention to or they would realize that the premise of being "given lemons" and the obvious sweet flavor and recipe of lemonade requires a magical step of phantasmagorical sugar.
When life gives you lemons... learn to juggle.
It's certainly something you can do with just lemons, I know, I learned to juggle with lemons. And it's certainly something people who have been given proverbial lemons learn to do well.