I can recommend against the Garnier Fruitics curl enhancing spray. It sucks! I'm mad I spend $3 on it!
I too have wavy hair when it air dries and wanted an easy wavy look for the summer. So, needless to say, I'll be paying close attention to this thread!
When I wear my hair wavy, I start with a curl-enhancing shampoo & conditioner, then when I get out of the shower I scrunch in Herbal Essences Totally Twisted curl-enhancing gel, then I "plop" like this:
(I'm at work and can't listen to what she says, but from watching it I think this video looks accurate)
Then I dry it by taking a section of hair, scrunching it up in a diffuser, and staying on that section until it's dry, then moving on to a new section.
I've tried a bunch of products but for me the process (plopping and diffusing) make the most difference. You might want to also look into the Curly Girl method (a few of us did it on here about a year ago, so you could probably do a search and find our thread or just google for info from others). It didn't work out for me but for a lot of people it totally transforms their hair.
(P.S. lately I've also been rag-rolling my hair overnight with creamier styling products because in the summer I hate using heat tools - although with rag rolling it really creates a curl more than encourages your own wave)
I have a tight wave to my hair. I use John Frieda Fizz Ease Spiral Spray when I want to let the wave happen. I spray it all over the hair and let it air dry or use the low setting on the hairdryer (I don't even know where my diffuser is.) If I brush it out while drying, the wave is looser. If I just let it air dry, the curls get tighter.
When it's dry, I'll run some glosser through my hair too to control any frizz.
I might start with the John Frieda spray. I'm looking for something quick & easy. I just don't have the time in the morning for too many steps. I started using Wen cleansing conditioner...it makes a difference for me. It has really brought out the natural movement my hair has and makes it feel a little thicker. I'm hoping to find a product that will boost what the Wen is doing for me.