It seems obvious in hindsight

A water bottle with a filling cap on the side.

We all know what a pain it is to wedge bottles upright in shallow sinks and the like. Come to think of it, the only bottles I remember being easy were the ones loaded into a Super Soaker.

The beautifully simple Binibottle is the work of 15-year-old Anna Axelsson of Sweden and the gold medal-winning design at the "Finn upp" inventor competition. It has the twist-off, pull-up cap you're used to up top but also an additional, recessed twist-off cap on the side so you can hold it sideways while you're filling it.