Nothing like a properly made Gin & Tonic to beat the heat. Also, a Dark 'n' Stormy, Margarita, Mojito, Tom Collins, or Gin Rickey. Basically, any well made cocktail of white rum, gin, or tequila. You don't want anything too strong. A good session beer is always an alternative.
As for food I prefer something that goes with the patio drinking. Grill up some sausages from Kramarczuk's, throw on some mustard and fried onions.