Custom sodas and syrups. They should be a thing. So why oh why are 98% of the syrups we see nothing more than extract from a bottle mixed with corn syrup? Some things will never make sense to me.
As you're making plans for summer entertaining, let me throw an idea out there. The last few years, Yoni and I have thrown a Soda Spash. It was supposed to be a splash, until I forgot the L in the sign and just decided to go with it. Here's how it works: make a vat of simple syrup and a vat of caramel. Then mix that with malt powder, peanut butter, and pretty much every ingredient listed above. Get ice cream, sparkling water and TADAH! Baller party with a fresh take on ice cream sodas. You don't have to go as crazy as I do on the syrups. Maybe start with one or two, then you can improvise from there. The options are as varied as your imagination, but this should give you a good start!
1 Part Sugar (I like to make one brown sugar batch and one white sugar batch)
1 Part Water
Boil sugar and water together until sugar dissolves and consistency is slightly syrupy. Usually 5-10 minutes. This keeps for a long time. No need to put it in the fridge either.
Salted Chocolate Syrup
1 Cup simple syrup + 1 Cup dark chocolate chips + 1 tsp salt (optional)
Warm simple syrup. Add dark chocolate slowly, stirring until melted into the syrup. Add salt. Cool, but allow to come to room temperature before serving. Store in the fridge.
Strawberry Malt Syrup
Simple syrup + Frozen strawberries + Malt powder
I'd try about 1/2 the amount of simple syrup as strawberries. Pulverize strawberries in blender with a few hefty tablespoons of malt powder. Add simple syrup and stir. Allow strawberries to melt and macerate in the simple syrup. Refrigerate in airtight container.
A FEW TIPS:
Try sodas with about 1/2 inch of syrup in a 6 oz cup. You can always make it sweeter.
Buy a large carton of whole milk, half and half or whipping cream and add a shot to make cream sodas. You can do this with any non-fruit syrup.
Sometimes we make the sodas on their own and sometimes we do ice cream sodas. I make my life easier by only getting one flavor of Ice Cream -- a good Vanilla. People can still go wild with the flavors but you have fewer variables involved.