Lets go further and synthesize them to even longer and more complex carbohydrates so that they will be liquid at normal temperature and smell nice!
If you abandon the "smell nice" constraint, you can get an even higher hydrogen mass fraction. For example, n-pentane has a hydrogen mass fraction of about 16.8% and it's liquid at a pressure of 1 atmosphere and a temperature of 25 degrees Celsius, but it evaporates rapidly, so you need to keep it in a container.
If you don't mind pressurizing the container a bit, you could put ammonia in there, and it has a hydrogen mass fraction of about 17.6%.