There are lots of patterns/tutorials available out there for sun hats, from the ones I saw I think they all tend to be free patterns and they don't need a large amount of fabric, so they're basically a very cheap make. I used this reversible bucket hat pattern and it was straight forward and fairly quick to make.
After making one for each of the girls I decided that I really needed one too. I had to enlarge the pattern for mine so if you're making a grown up one you might be better finding a different source for your pattern.
Maria's hat was made from part of a thrifted shirt and an old sheet, mine from a slightly strange, reversible, thrifted scarf, and Venetia chose some 'new' fabric which I've had sitting around for several years, with her contrasting fabric coming from an old napkin which just happened to be the perfect shade.
Maria and I both prefer our hats one particular way, but Venetia likes changing hers up with the reversible nature of it.
I can see myself making a few more of these before Summer hits properly, Venetia in particular will want to be able to colour coordinate with her outfit, and we all have a tendency to mislay such things, so basically there's no such thing as too many sun hats around here!
Especially if you wear three at once!